feat(views): Phase 5j slice C — full URL migration + system views

Per m's Q1 pick (b) (2026-05-29): legacy `/`, `/dashboard`, `/calendar`,
`/timeline`, `/graph` become `/views/{system-slug}`. Old routes
301-redirect to the new ones with chip params preserved; the legacy
?view=<uuid> param from 5i is resolved through the uuid → slug map
when present so old bookmarks land on the right user view.

System views (web/system_views.go):
- SystemView struct (Slug / Name / Icon / URL) — code-resident, never
  rows in projax.views.
- AllSystemViews() returns the canonical five: tree, dashboard,
  calendar, timeline, graph. Display order matches the existing
  sidebar.
- LookupSystemView(slug) returns the matching entry or nil; the
  reserved-slug list in store.IsReservedViewSlug (slice A) is kept
  in sync.
- legacyRedirect(systemSlug) handler 301s with chip-param preservation
  + uuid → slug resolution for any leftover ?view=<uuid>.

Routes (web/server.go):
- GET /views/tree      → handleTree     (was GET /)
- GET /views/dashboard → handleDashboard
- GET /views/timeline  → handleTimeline
- GET /views/calendar  → handleCalendar
- GET /views/graph     → handleGraph
- GET /                → 301 → /views/tree
- GET /dashboard       → 301 → /views/dashboard
- GET /timeline        → 301 → /views/timeline
- GET /calendar        → 301 → /views/calendar
- GET /graph           → 301 → /views/graph
- POST action endpoints (/dashboard/task/*, /dashboard/pin, /admin/*)
  stay where they are — those are RPC-ish, not page renders.

handleTree: dropped the `r.URL.Path != "/"` guard — the only entry
point now is /views/tree, mounted via the new route. Slice F removes
any residual references; this slice keeps the handler reachable.

computeChipCounts grew a `base string` arg so chip URLs anchor on the
caller's route (/views/tree for the system tree, /views/{slug} for
saved views). PageViewTypes recognises both legacy and /views/ keys
during the transition.

Template hrefs / hx-gets bulk-updated to the new URLs:
- layout.tmpl: every sidebar + bottom-nav entry points at
  /views/{system-slug}. Active-state checks updated alongside.
- tree_section.tmpl, tree_card.tmpl, tree_kanban.tmpl: clear-filter
  / clear-all hrefs → /views/tree.
- calendar*.tmpl, timeline_section.tmpl, graph.tmpl,
  dashboard_section.tmpl: every internal nav + filter link points at
  the /views/{slug} surface.
- detail.tmpl, error.tmpl: cancel / back-to-tree → /views/tree.

Test-source updates (per the 5c sharpened rule):
- ~100 test paths bulk-rewritten from /dashboard /calendar /timeline
  /graph (and `/`) to their /views/{slug} counterparts. The
  behaviour-preservation contract holds: status codes + body shapes
  for the rendered pages stay the same; only the URL anchoring the
  test changes.
- layout_test.go: sidebar href assertions updated to /views/{slug}.
- view_type_test.go (Q2 + Q3 follow-up): PageViewTypes lookup table
  updated to use the new route keys.
- 2 deliberate behaviour-change assertions land: TestLegacyRedirects
  expects 301 on the old URLs (was 200); TestTreeRenders fetches
  /views/tree (the new home) instead of /.

Internal go-source URL emissions (dashboard.go, calendar.go,
timeline.go) updated to the new BasePath so chip + refresh URLs round
through /views/{slug} correctly.

New tests:
- TestSystemViewLookup — AllSystemViews shape + LookupSystemView
  round-trip + unknown-slug nil.
- TestLegacyRedirects — every legacy URL 301s to its new home with
  chip params preserved.
- TestLegacyViewUUIDRedirect — old `?view=<uuid>` URLs land on the
  resolved slug per m's Q3 pick.

web/server_test.go

@@ -81,9 +81,9 @@ func TestTreeRenders(t *testing.T) {
 	srv, pool := mustServer(t)
 	defer pool.Close()
 	h := srv.Routes()
-	code, body := get(t, h, "/")
+	code, body := get(t, h, "/views/tree")
 	if code != 200 {
-		t.Fatalf("GET / status %d body=%s", code, body)
+		t.Fatalf("GET /views/tree status %d body=%s", code, body)
 	}
 	// /admin/classify used to live in the nav; Phase 3o consolidated all
 	// admin links under the new /admin index. Assert /admin instead.
@@ -102,7 +102,7 @@ func TestLayoutHasViewportMeta(t *testing.T) {
 	srv, pool := mustServer(t)
 	defer pool.Close()
 	h := srv.Routes()
-	for _, path := range []string{"/", "/dashboard", "/calendar", "/graph", "/admin/bulk", "/admin/classify", "/new", "/login"} {
+	for _, path := range []string{"/views/tree", "/views/dashboard", "/views/calendar", "/views/graph", "/admin/bulk", "/admin/classify", "/new", "/login"} {
 		_, body := get(t, h, path)
 		if !strings.Contains(body, `name="viewport"`) {
 			t.Errorf("GET %s: missing <meta name=\"viewport\">", path)
@@ -302,7 +302,7 @@ func TestTreeRendersKanbanWhenViewTypeIsKanban(t *testing.T) {
 	srv, pool := mustServer(t)
 	defer pool.Close()
 	h := srv.Routes()
-	_, body := get(t, h, "/?view_type=kanban")
+	_, body := get(t, h, "/views/tree?view_type=kanban")
 	if !strings.Contains(body, `class="kanban-board"`) {
 		t.Error("?view_type=kanban should render the kanban board")
 	}
@@ -324,7 +324,7 @@ func TestTreeRendersCardGridWhenViewTypeIsCard(t *testing.T) {
 	defer pool.Close()
 	h := srv.Routes()
 	// List view (default): forest markup expected; tree-card-grid absent.
-	_, listBody := get(t, h, "/")
+	_, listBody := get(t, h, "/views/tree")
 	if !strings.Contains(listBody, `<ul class="forest">`) {
 		t.Error("default GET / should render the tree forest")
 	}
@@ -335,7 +335,7 @@ func TestTreeRendersCardGridWhenViewTypeIsCard(t *testing.T) {
 		t.Error("view-type chip strip should appear on every view")
 	}
 	// Card view: card grid present, forest absent.
-	_, cardBody := get(t, h, "/?view_type=card")
+	_, cardBody := get(t, h, "/views/tree?view_type=card")
 	if !strings.Contains(cardBody, `class="tree-card-grid"`) {
 		t.Error("GET /?view_type=card should render the card grid")
 	}
@@ -343,7 +343,7 @@ func TestTreeRendersCardGridWhenViewTypeIsCard(t *testing.T) {
 		t.Error("GET /?view_type=card should not render the tree forest")
 	}
 	// Unknown view_type falls back to list.
-	_, unknownBody := get(t, h, "/?view_type=junk")
+	_, unknownBody := get(t, h, "/views/tree?view_type=junk")
 	if !strings.Contains(unknownBody, `<ul class="forest">`) {
 		t.Error("unknown view_type should fall back to list")
 	}
@@ -393,7 +393,7 @@ func TestProjectFilterScopesTreeToDescendants(t *testing.T) {
 	siblingLink := `href="/i/dev.` + siblingSlug + `"`
 
 	// Descendants on (default): parent + child visible, sibling hidden.
-	_, withDesc := get(t, h, "/?project="+parentPath)
+	_, withDesc := get(t, h, "/views/tree?project="+parentPath)
 	if !strings.Contains(withDesc, parentLink) {
 		t.Errorf("?project=%s should show parent row", parentPath)
 	}
@@ -405,7 +405,7 @@ func TestProjectFilterScopesTreeToDescendants(t *testing.T) {
 	}
 
 	// Descendants off: only the picked item, no children.
-	_, noDesc := get(t, h, "/?project="+parentPath+"&project_descendants=0")
+	_, noDesc := get(t, h, "/views/tree?project="+parentPath+"&project_descendants=0")
 	if !strings.Contains(noDesc, parentLink) {
 		t.Errorf("?project_descendants=0 should still show the picked parent row")
 	}