hooks: two-tier design hook — immediate per-edit rules + full-set Stop deep pass

Eval evidence showed the per-edit PostToolUse stream fires overwhelmingly
on copy-level rules (em-dash-overuse ~97x/session) and measurably makes
models more conservative, while a full-detector pass at completion is what
actually fixes contrast/padding/glow. Split the hook accordingly:

- Per-edit (PostToolUse) now surfaces only IMMEDIATE_TIER_RULES: broken
  output (broken-image, text-overflow, clipped-overflow-container,
  body-text-viewport-edge), objective contrast/legibility failures
  (low-contrast, gray-on-color, tiny-text), single-property mechanical
  slop (gradient-text, dark-glow), and design-system drift (the four
  design-system-* rules, which compound if left uncorrected). Everything
  else defers. Override with hook.perEditRules: "all" in
  .impeccable/config.json. Tiering is off for Cursor/Copilot harnesses,
  which have no Stop pass wired, so nothing gets silently dropped there.

- Stop deep pass (runStopHook): runs the FULL rule set over every UI file
  touched this session (tracked via the existing hook.cache.json session
  state; deferred-only edits now mark the file touched), dedupes against
  everything already surfaced per-edit, honors ignore-rule/file/value and
  inline disables, reuses the [impeccable@1] envelope, and no-ops fast
  when no UI files were touched. Emits hookSpecificOutput
  { hookEventName: "Stop", additionalContext } per the Claude Code SDK
  Stop contract (conversation continues so the model can act on it).
  Second Stop fire is silent - deep-pass findings are remembered.

- Wiring: Stop entries (timeout 30) in plugin/hooks/hooks.json, the
  .claude settings + .codex hooks manifests (transformers + hook-admin
  repair path). Claude Code and Codex both dispatch a native Stop event;
  Cursor's stop hook is inconsistently dispatched (pre-write gate stays)
  and Copilot's agentStop/sessionEnd don't inject model context, so
  neither gets a Stop entry - documented in reference/hooks.md.

- Tests: tiering split/override/harness gating, Stop dedupe + silent
  no-touched-files + ignore machinery + kill switches; existing per-edit
  tests moved to immediate-tier rule ids. 181 tests green; smoke-tested
  the built dist skill end to end (glow surfaced per-edit, em-dash only
  at Stop, second Stop silent).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

skill/scripts/hook.mjs

@@ -1,19 +1,25 @@
 #!/usr/bin/env node
 /**
- * Impeccable design hook — PostToolUse entry point.
+ * Impeccable design hook — PostToolUse + Stop entry point.
  *
- * Reads the Claude Code / Codex / Cursor hook event from stdin, runs the design
- * detector against the touched file, and emits a system reminder via
- * `hookSpecificOutput.additionalContext` when findings exist.
+ * Reads the Claude Code / Codex / Cursor hook event from stdin and routes by
+ * `hook_event_name`:
+ *
+ *   - PostToolUse: runs the immediate-tier detector rules against the touched
+ *     file and emits a system reminder via
+ *     `hookSpecificOutput.additionalContext` when findings exist.
+ *   - Stop: runs the FULL detector rule set over every UI file touched this
+ *     session (the deep pass), deduped against what the per-edit pass already
+ *     surfaced, and emits once via the Stop additionalContext channel.
  *
  * Contract: never break a turn. Always exit 0. Clean files emit a small ack
- * unless quiet mode is enabled.
+ * unless quiet mode is enabled; a clean Stop pass is silent.
  *
  * Most logic lives in `hook-lib.mjs` so it is unit-testable without a
  * subprocess. This file is the thin stdin/stdout adapter.
  */
 
-import { runHook, writeAuditLog } from './hook-lib.mjs';
+import { runHook, runStopHook, writeAuditLog } from './hook-lib.mjs';
 
 async function readStdin() {
   if (process.stdin.isTTY) return '';
@@ -22,6 +28,16 @@ async function readStdin() {
   return Buffer.concat(chunks).toString('utf-8');
 }
 
+function isStopEvent(stdinJson) {
+  try {
+    const event = JSON.parse(stdinJson);
+    return event && typeof event === 'object' && event.hook_event_name === 'Stop';
+  } catch {
+    // Malformed stdin falls through to runHook, which audits the skip.
+    return false;
+  }
+}
+
 async function main() {
   // Snapshot the inherited env FIRST so the re-entrancy guard checks the
   // parent's value, not the value we are about to export for any child
@@ -32,7 +48,8 @@ async function main() {
   let stdinJson = '';
   try { stdinJson = await readStdin(); } catch { /* fall through */ }
 
-  const result = await runHook({
+  const run = isStopEvent(stdinJson) ? runStopHook : runHook;
+  const result = await run({
     stdinJson,
     env: inheritedEnv,
     cwd: process.cwd(),
@@ -50,7 +67,7 @@ main().catch((err) => {
   try {
     writeAuditLog(process.env, {
       ts: new Date().toISOString(),
-      event: 'PostToolUse',
+      event: 'hook-error',
       error: String(err && err.message ? err.message : err),
     });
   } catch { /* swallow */ }