feat: Go HTTP server with tree / detail / new / classify

cmd/projax/main.go boots a pgxpool against PROJAX_DB_URL (falls back to
SUPABASE_DATABASE_URL), auto-applies embedded migrations on start
(disable with PROJAX_AUTO_MIGRATE=off), and serves on PROJAX_LISTEN_ADDR
(default :8080).

store package wraps the unified view + projax.items writes. Item has
helper methods for templates: IsArea, Editable, SourceRefDeref. The
Promote() flow runs the insert + item_links link inside a single
transaction so the source row drops out of items_unified atomically.

web package: per-page html/template instances parsed against a shared
layout.tmpl, embedded static/style.css, HTMX from CDN. Pages:
  GET  /                   tree of items_unified
  GET  /i/{path}           detail (editable for projax, read-only +
                           promote form for mai.projects)
  POST /i/{path}           update projax-native item
  POST /i/{path}/promote   one-page promote (HTMX-aware fragment for
                           inline classify)
  GET  /new?parent={path}  create form
  POST /new                create projax-native item
  GET  /admin/classify     orphan list with inline HTMX promote
  GET  /healthz            DB ping
  GET  /static/*           embedded assets

Auth is intentionally out of scope for v1 — service binds to whatever
PROJAX_LISTEN_ADDR points at, deploy guidance pins it to the Tailscale
interface (covered in 1d README).

Tests (skip when DB env is unset):
  TestTreeRenders, TestHealthz,
  TestDetailProjaxNativeEditable, TestDetailMaiProjectsReadOnly,
  TestClassifyListsOrphans, TestPromoteRoundTrip.

web/templates/classify.tmpl

@@ -0,0 +1,37 @@
+{{define "content"}}
+<h1>Classify mai.projects orphans</h1>
+<p>{{len .Orphans}} unclassified rows. Pick an area (or any projax item) per row and click Promote — keeps the original mai.projects row untouched and links back via item_links.</p>
+
+<table class="classify">
+  <thead>
+    <tr><th>Mai ID / Title</th><th>Status</th><th>Parent</th><th>Slug</th><th>Title</th><th></th></tr>
+  </thead>
+  <tbody>
+    {{range .Orphans}}
+      <tr id="row-{{.SourceRefDeref}}">
+        <td>
+          <a href="/i/{{.Path}}">{{.Title}}</a>
+          <br><small class="slug">{{.SourceRefDeref}}</small>
+        </td>
+        <td><span class="status status-{{.Status}}">{{.Status}}</span></td>
+        <td>
+          <form
+            hx-post="/i/{{.Path}}/promote"
+            hx-target="#row-{{.SourceRefDeref}}"
+            hx-swap="outerHTML"
+            class="inline-promote">
+            <select name="parent_id" required>
+              <option value="">— pick parent —</option>
+              {{range $.ParentOptions}}<option value="{{.ID}}">{{.Path}}</option>{{end}}
+            </select>
+        </td>
+        <td><input name="slug" value="{{.Slug}}" required pattern="[^.]+"></td>
+        <td><input name="title" value="{{.Title}}" required></td>
+        <td><button type="submit">Promote</button></form></td>
+      </tr>
+    {{else}}
+      <tr><td colspan="6"><em>No orphans. Everything is classified.</em></td></tr>
+    {{end}}
+  </tbody>
+</table>
+{{end}}

web/templates/detail.tmpl

@@ -0,0 +1,71 @@
+{{define "content"}}
+<h1>{{.Item.Title}}</h1>
+<p class="meta">
+  <span class="source source-{{.Item.Source}}">{{.Item.Source}}</span>
+  <span class="slug">{{.Item.Path}}</span>
+  <span class="status status-{{.Item.Status}}">{{.Item.Status}}</span>
+  {{if .Item.Pinned}}<span class="pin">pinned</span>{{end}}
+  {{if .Item.Archived}}<span class="archived">archived</span>{{end}}
+</p>
+
+{{if .Item.Editable}}
+  <form method="post" action="/i/{{.Item.Path}}" class="edit">
+    <label>Title <input name="title" value="{{.Item.Title}}" required></label>
+    <label>Slug <input name="slug" value="{{.Item.Slug}}" required pattern="[^.]+"></label>
+    <label>Parent
+      <select name="parent_id">
+        {{if .Item.IsArea}}
+          <option value="" selected>(root area)</option>
+        {{else}}
+          {{range .ParentOptions}}
+            <option value="{{.ID}}" {{if and $.Item.ParentID (eq .ID (deref $.Item.ParentID))}}selected{{end}}>{{.Path}}</option>
+          {{end}}
+        {{end}}
+      </select>
+    </label>
+    <label>Status
+      <select name="status">
+        {{range $opt := .StatusOptions}}
+          <option value="{{$opt}}" {{if eq $opt $.Item.Status}}selected{{end}}>{{$opt}}</option>
+        {{end}}
+      </select>
+    </label>
+    <label class="checkbox">
+      <input type="checkbox" name="pinned" value="1" {{if .Item.Pinned}}checked{{end}}> pinned
+    </label>
+    <label class="checkbox">
+      <input type="checkbox" name="archived" value="1" {{if .Item.Archived}}checked{{end}}> archived
+    </label>
+    <label>Content
+      <textarea name="content_md" rows="14">{{.Item.ContentMD}}</textarea>
+    </label>
+    <div class="actions">
+      <button type="submit">Save</button>
+      <a class="cancel" href="/">Cancel</a>
+    </div>
+  </form>
+{{else}}
+  <div class="readonly">
+    <p><em>Read-only: this row is sourced from {{.Item.Source}}.</em></p>
+    <pre class="content">{{.Item.ContentMD}}</pre>
+
+    <h2>Promote to projax</h2>
+    <p>Pick the area or project this should live under. mai.projects row stays untouched; the projax item links back to it via item_links.</p>
+    <form method="post" action="/i/{{.Item.Path}}/promote" class="promote">
+      <label>Parent
+        <select name="parent_id" required>
+          {{range .ParentOptions}}
+            <option value="{{.ID}}">{{.Path}}</option>
+          {{end}}
+        </select>
+      </label>
+      <label>Slug <input name="slug" value="{{.Item.Slug}}" required pattern="[^.]+"></label>
+      <label>Title <input name="title" value="{{.Item.Title}}" required></label>
+      <div class="actions">
+        <button type="submit">Promote</button>
+        <a class="cancel" href="/">Cancel</a>
+      </div>
+    </form>
+  </div>
+{{end}}
+{{end}}

web/templates/error.tmpl

@@ -0,0 +1,5 @@
+{{define "content"}}
+<h1>Error</h1>
+<p class="error">{{.Message}}</p>
+<p><a href="/">Back to tree</a></p>
+{{end}}

web/templates/layout.tmpl

@@ -0,0 +1,20 @@
+{{define "layout"}}<!doctype html>
+<html lang="en">
+<head>
+<meta charset="utf-8">
+<title>{{.Title}} — projax</title>
+<link rel="stylesheet" href="/static/style.css">
+<script src="https://unpkg.com/htmx.org@1.9.12" integrity="sha384-ujb1lZYygJmzgSwoxRggbCHcjc0rB2XoQrxeTUQyRjrOnlCoYta87iKBWq3EsdM2" crossorigin="anonymous"></script>
+</head>
+<body>
+<header>
+  <nav>
+    <a href="/" class="brand">projax</a>
+    <a href="/admin/classify">classify orphans</a>
+  </nav>
+</header>
+<main>
+{{template "content" .}}
+</main>
+</body>
+</html>{{end}}

web/templates/new.tmpl

@@ -0,0 +1,28 @@
+{{define "content"}}
+<h1>New item</h1>
+<p class="meta">Parent: <strong>{{if .Parent}}{{.Parent.Path}}{{else}}(root area){{end}}</strong></p>
+
+<form method="post" action="/new" class="edit">
+  {{if .Parent}}<input type="hidden" name="parent_id" value="{{.Parent.ID}}">{{end}}
+  <label>Kind
+    <select name="kind">
+      {{if not .Parent}}<option value="area" selected>area</option>{{end}}
+      <option value="project" {{if .Parent}}selected{{end}}>project</option>
+    </select>
+  </label>
+  <label>Title <input name="title" required></label>
+  <label>Slug <input name="slug" required pattern="[^.]+" placeholder="lowercase, no dots"></label>
+  <label>Status
+    <select name="status">
+      {{range $opt := .StatusOptions}}<option value="{{$opt}}">{{$opt}}</option>{{end}}
+    </select>
+  </label>
+  <label>Content
+    <textarea name="content_md" rows="10"></textarea>
+  </label>
+  <div class="actions">
+    <button type="submit">Create</button>
+    <a class="cancel" href="{{if .Parent}}/i/{{.Parent.Path}}{{else}}/{{end}}">Cancel</a>
+  </div>
+</form>
+{{end}}

web/templates/tree.tmpl

@@ -0,0 +1,52 @@
+{{define "content"}}
+<h1>Tree</h1>
+<p class="counts">
+  <strong>{{.ProjaxCount}}</strong> projax · <strong>{{.MaiCount}}</strong> mai.projects orphans
+  {{if .MaiCount}}<a href="/admin/classify">→ classify</a>{{end}}
+</p>
+
+<section class="tree">
+  <h2>Areas + projax items</h2>
+  <ul class="forest">
+    {{range .Areas}}
+      <li class="node area">
+        <a href="/i/{{.Item.Path}}">{{.Item.Title}}</a>
+        <span class="slug">{{.Item.Path}}</span>
+        <a class="add" href="/new?parent={{.Item.Path}}">+</a>
+        {{template "children" .}}
+      </li>
+    {{end}}
+  </ul>
+</section>
+
+{{if .Orphans}}
+<section class="orphans">
+  <h2>mai.projects orphans <small>(unclassified)</small></h2>
+  <ul class="flat">
+    {{range .Orphans}}
+      <li class="node orphan">
+        <a href="/i/{{.Path}}">{{.Title}}</a>
+        <span class="slug">{{.Path}}</span>
+        <span class="status status-{{.Status}}">{{.Status}}</span>
+      </li>
+    {{end}}
+  </ul>
+</section>
+{{end}}
+{{end}}
+
+{{define "children"}}
+  {{if .Children}}
+    <ul>
+      {{range .Children}}
+        <li class="node project">
+          <a href="/i/{{.Item.Path}}">{{.Item.Title}}</a>
+          <span class="slug">{{.Item.Path}}</span>
+          <span class="status status-{{.Item.Status}}">{{.Item.Status}}</span>
+          <a class="add" href="/new?parent={{.Item.Path}}">+</a>
+          {{template "children" .}}
+        </li>
+      {{end}}
+    </ul>
+  {{end}}
+{{end}}