feat(spec): carve the post-confirmation gate-and-file tail into one section

Phases 1-4 are the turn-1 conversational spine — carving them would force the
Read on the first user message for zero real savings. The mechanical tail
(4.5/4.5a/4.5b redaction gates + Phase 5 filing + TTHW telemetry) fires only
after draft confirmation: a genuine lazy boundary, kept as ONE section so the
gh-issue-create bash can never load without the fail-closed redaction gate
that precedes it. Skeleton 65.4KB -> 50.7KB; all ~85 phase-structure
invariants migrated location-aware plus a new carve-shape suite (56 tests).

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

spec/sections/manifest.json

@@ -0,0 +1,14 @@
+{
+  "$schema": "https://gstack.dev/schemas/section-manifest.json",
+  "skill": "spec",
+  "version": 1,
+  "note": "PASSIVE registry (v2 plan T9 / CM2). Fields are IDs, file paths, human titles, and human-readable trigger text ONLY. The skeleton's decision-tree prose is the ONLY place that decides WHEN to read a section; required-reads live in the E2E fixtures. No machine predicate here — see docs/designs/v2_PLAN.md:663.",
+  "sections": [
+    {
+      "id": "gate-and-file",
+      "file": "gate-and-file.md",
+      "title": "Quality gate, redaction, and filing (Phases 4.5-5)",
+      "trigger": "running the quality gate and filing the spec (Phases 4.5-5, once the user confirms the Phase 4 draft)"
+    }
+  ]
+}