feat(fristenrechner): Slice S6 — drop cascade endpoint, neutralize legacy Pathway B (m/paliad#146)

Cleanup pass per design §7 / S6, executed as a measured first cut
that drops the cascade endpoint + neutralizes the legacy Pathway B
row-stack / cascade init without lifting the entire ~1500 LoC
subtree out of `fristenrechner.ts`. The dead helpers stay for one
follow-up that can lift them safely.

Backend:
  * Deleted `internal/handlers/fristenrechner_event_categories.go`.
  * Dropped the `GET /api/tools/fristenrechner/event-categories`
    route from `handlers.go`. The `EventCategoryService` itself
    stays — it still backs the legacy concept-card search's
    `?event_category_slug=` filter, which dies in the same
    follow-up that removes the concept-card response shape.
  * `paliad.event_categories` TABLE is untouched per design §7
    (kept for future tools).

Frontend:
  * `loadEventCategoryTree()` reduced to a stub returning `[]` — the
    endpoint it fetched no longer exists, and no overhaul surface
    calls it.
  * `initB1Cascade()`, `initForumFilter()`, `initInboxFilter()`
    early-return. Their `DOMContentLoaded` registrations stay so
    the bundle exports are stable, but no Pathway B cascade /
    chip-strip / inbox-channel wiring fires in `?legacy=1` mode.
  * The Pathway B markup in `fristenrechner.tsx` stays in place; it
    renders inert when a user hits `?legacy=1&path=b`.
  * `buildRowStack`, `renderRowStack`, `runB1Search`, and the row-
    stack helper functions remain as unreachable code. Removing
    them mechanically requires retiring the entire upper-half
    Pathway B B2 search wiring (`runSearch` + `renderConceptCard`
    + `renderSearchResults` + `SearchResponse` types) which is
    tangled with the legacy concept-card response shape — deferred
    to a follow-up that lands together with the backend
    concept-card removal.

Verified — bun build clean (2971 i18n keys unchanged), 256
frontend tests pass, go build + vet clean, live-DB tests
(TestListProceedings, TestSearchEvents, TestLookupFollowUps)
still green.

Follow-up scope tracked in design §7 S6 — pending the helper-tree
lift and the legacy concept-card response-shape removal from
/search.

frontend/src/client/fristenrechner.ts

@@ -2655,33 +2655,16 @@ interface EventCategoryNode {
 let eventCategoryTree: EventCategoryNode[] | null = null;
 let eventCategoryFetchInflight: Promise<EventCategoryNode[]> | null = null;
 
-// Top-level cascade roots that represent forward-looking workflows ("I
+// t-paliad-323 Slice S6: the cascade endpoint
-// want to file X, what deadlines does my action trigger?") rather than
+// /api/tools/fristenrechner/event-categories was retired alongside
-// the backward-looking calc the Fristenrechner is built for ("event Y
+// HIDDEN_CASCADE_ROOTS. loadEventCategoryTree stays as a stub that
-// happened, what deadlines spawn?"). m's 2026-05-20 ask (m/paliad#57):
+// returns an empty tree — every caller below it sits in the legacy
-// remove these from the "Was ist passiert?" picker — they belong in a
+// Pathway B cascade which `?legacy=1` mode never boots into after
-// future forward-workflow tool, not here. The DB rows stay so that
+// initB1Cascade's early-return guard (see L3598). The whole subtree
-// future tool can pick them back up; we just hide them at the UI layer.
+// is dead-coded; a follow-up will lift it out wholesale.
-const HIDDEN_CASCADE_ROOTS: ReadonlySet<string> = new Set([
-  "ich-moechte-einreichen",
-]);
-
 async function loadEventCategoryTree(): Promise<EventCategoryNode[]> {
-  if (eventCategoryTree) return eventCategoryTree;
+  eventCategoryTree = [];
-  if (eventCategoryFetchInflight) return eventCategoryFetchInflight;
+  return eventCategoryTree;
-  eventCategoryFetchInflight = (async () => {
-    try {
-      const r = await fetch("/api/tools/fristenrechner/event-categories");
-      if (!r.ok) throw new Error(`HTTP ${r.status}`);
-      const data = await r.json();
-      const raw = (data.tree || []) as EventCategoryNode[];
-      eventCategoryTree = raw.filter((n) => !HIDDEN_CASCADE_ROOTS.has(n.slug));
-      return eventCategoryTree;
-    } finally {
-      eventCategoryFetchInflight = null;
-    }
-  })();
-  return eventCategoryFetchInflight;
 }
 
 function readB1PathFromURL(): string {
@@ -3596,30 +3579,14 @@ async function loadAndRenderB1() {
 }
 
 async function initB1Cascade() {
-  const panel = document.getElementById("fristen-b1-panel");
+  // t-paliad-323 Slice S6: the legacy Pathway B row-stack / cascade
-  if (!panel) return;
+  // is dead-coded. Mode A (S3) + Mode B wizard (S4) replace it; the
-
+  // overhaul default boot (S5) handles every user route. Early-return
-  // t-paliad-180: mode-radio retired; the row-stack's mode-row click
+  // here keeps the legacy module imports linked (for ?legacy=1 entry)
-  // handler drives tree↔filter routing. No standalone change listener
+  // while ensuring no cascade fetch / row-stack render fires. The
-  // needed here — showBMode() triggers loadAndRenderB1 when the
+  // helper bodies stay for one cleanup follow-up that lifts the whole
-  // pathway enters tree mode.
+  // subtree out.
-
+  return;
-  // Initial render if the URL already lands in tree mode.
-  const sp = new URLSearchParams(window.location.search);
-  if (sp.get("path") === "b" && sp.get("mode") === "tree") {
-    loadAndRenderB1();
-  }
-
-  // popstate restores the cascade depth.
-  window.addEventListener("popstate", () => {
-    const params = new URLSearchParams(window.location.search);
-    if (params.get("path") === "b" && params.get("mode") === "tree") {
-      // Always re-render — tree may not have loaded yet on first popstate.
-      currentActiveRow = null;
-      cascadeAutoWalkStopAfter = null;
-      loadAndRenderB1();
-    }
-  });
 }
 
 document.addEventListener("DOMContentLoaded", initB1Cascade);
@@ -3720,23 +3687,11 @@ function getActiveForumsParam(): string {
 }
 
 function initForumFilter() {
-  // Hydrate from URL on first load.
+  // t-paliad-323 Slice S6: dead-coded alongside initB1Cascade. The
-  for (const slug of readForumsFromURL()) {
+  // legacy forum-chip strip lived in the Pathway B B2-search panel
-    activeForums.add(slug);
+  // which the overhaul has retired. Helper bodies stay for the
-  }
+  // follow-up cleanup that lifts the whole Pathway B subtree.
-  renderForumChips();
+  return;
-
-  // Restore on browser nav.
-  window.addEventListener("popstate", () => {
-    activeForums.clear();
-    for (const slug of readForumsFromURL()) {
-      activeForums.add(slug);
-    }
-    renderForumChips();
-  });
-
-  // Re-render labels on language change.
-  onLangChange(() => renderForumChips());
 }
 
 document.addEventListener("DOMContentLoaded", initForumFilter);
@@ -4020,49 +3975,11 @@ async function persistInboxPref(ch: InboxChannel) {
 }
 
 async function initInboxFilter() {
-  // t-paliad-180: the standalone inbox chip strip is retired; inbox
+  // t-paliad-323 Slice S6: dead-coded alongside initB1Cascade /
-  // state still drives cascade narrowing + B2 fine-bucket sync, just
+  // initForumFilter. The inbox-channel row lived inside Pathway B's
-  // surfaced through the row-stack row now. This init still hydrates
+  // row-stack which the overhaul has retired. Helper bodies stay
-  // from URL / saved preference + wires the popstate restore.
+  // for the follow-up cleanup that lifts the whole subtree.
-  if (!document.getElementById("fristen-b1-panel")) return;
+  return;
-
-  let initial: InboxChannel = readInboxFromURL();
-  if (initial === null) {
-    try {
-      const resp = await fetch("/api/me", { credentials: "same-origin" });
-      if (resp.ok) {
-        const me = (await resp.json()) as { forum_pref?: string | null };
-        if (me.forum_pref && INBOX_CHANNEL_VALUES.has(me.forum_pref)) {
-          initial = me.forum_pref as InboxChannel;
-        }
-      }
-    } catch {
-      // Anonymous visitor or transient error — leave the chip unset.
-    }
-  }
-  applyInboxFilter(initial);
-
-  // Sync B2 fine-bucket chips from the inbox on hydrate ONLY when the
-  // URL doesn't explicitly carry ?forum=… — an explicit forum= comes
-  // from a shared link and should win over the user's saved inbox
-  // preference. initForumFilter (which runs first) has already
-  // populated activeForums from URL forum=, so we leave it alone here.
-  if (initial !== null && readForumsFromURL().length === 0) {
-    applyFineForumsFromInbox(initial);
-    writeForumsToURL(true);
-  }
-
-  window.addEventListener("popstate", () => {
-    const newInbox = readInboxFromURL();
-    applyInboxFilter(newInbox);
-    // popstate can land on a URL with inbox= but no forum= (the user
-    // navigated to a state where derivation should re-apply). Don't
-    // touch activeForums when forum= is explicit — initForumFilter's
-    // own popstate handler has already loaded it from the URL.
-    if (newInbox !== null && readForumsFromURL().length === 0) {
-      applyFineForumsFromInbox(newInbox);
-    }
-  });
 }
 
 document.addEventListener("DOMContentLoaded", initInboxFilter);

internal/handlers/fristenrechner_event_categories.go

@@ -1,31 +0,0 @@
-package handlers
-
-import (
-	"net/http"
-)
-
-// GET /api/tools/fristenrechner/event-categories — returns the full
-// decision-tree taxonomy for the v3 Pathway B / B1 cascade UI
-// (t-paliad-133). Tree is small (~100 nodes) and mostly static; the
-// frontend ETag-caches it via localStorage.
-//
-// Returns 503 if the DB-backed services aren't wired (DATABASE_URL
-// unset).
-func handleFristenrechnerEventCategories(w http.ResponseWriter, r *http.Request) {
-	if dbSvc == nil || dbSvc.eventCategory == nil {
-		writeJSON(w, http.StatusServiceUnavailable, map[string]string{
-			"error": "Decision-tree-Taxonomie vorübergehend nicht verfügbar (keine Datenbank).",
-		})
-		return
-	}
-	tree, err := dbSvc.eventCategory.Tree(r.Context())
-	if err != nil {
-		writeJSON(w, http.StatusInternalServerError, map[string]string{
-			"error": "Decision-tree fehlgeschlagen: " + err.Error(),
-		})
-		return
-	}
-	writeJSON(w, http.StatusOK, map[string]any{
-		"tree": tree,
-	})
-}

internal/handlers/handlers.go

@@ -308,7 +308,13 @@ func Register(mux *http.ServeMux, client *auth.Client, giteaAPIToken string, svc
 	protected.HandleFunc("GET /api/tools/courts", handleCourtsList)
 	protected.HandleFunc("GET /api/tools/fristenrechner/search", handleFristenrechnerSearch)
 	protected.HandleFunc("GET /api/tools/fristenrechner/follow-ups", handleFristenrechnerFollowUps)
-	protected.HandleFunc("GET /api/tools/fristenrechner/event-categories", handleFristenrechnerEventCategories)
+	// t-paliad-323 Slice S6: the cascade endpoint /api/tools/fristenrechner/
+	// event-categories is retired — the Fristenrechner overhaul Mode A
+	// + wizard surfaces don't read the event_categories taxonomy. The
+	// table itself stays for future tools (design doc §7). The
+	// EventCategoryService still backs the /search endpoint's legacy
+	// ?event_category_slug filter; that filter is dead-coded too but
+	// removing the service is a separate follow-up.
 	protected.HandleFunc("GET /downloads", handleDownloadsPage)
 	protected.HandleFunc("GET /glossary", handleGlossaryPage)
 	protected.HandleFunc("GET /api/glossary", handleGlossaryAPI)