Slice 8: v1 ships — integration coverage, runbook, spec corrections

- Five new integration test files raise the suite from 75 to 96 green:
  test_hygiene_vertical (7), test_branch_path_routing (4),
  test_metadata_pr_merge (3), test_cache_bootstrap (4), test_e2e_smoke
  (3). The smoke test walks propose → super-draft → edit branch →
  body-edit PR → graduate → active-RFC PR → merge → notification →
  hygiene-sweep deletion end-to-end.
- deploy/RUNBOOK.md replaces the prior DEPLOY.md stub as a real
  runbook: prerequisites, first-time bring-up, day-2 ops (logs, DB
  backup, secret rotation, the §12 hygiene cadence), rollback shape,
  troubleshooting table.
- backend/.env.example grows the SMTP block, HYGIENE_TICK_SECONDS,
  and WEBHOOK_EMAIL_BOUNCE_SECRET with inline commentary.
- README points to RUNBOOK.md; the "what the build lets you do"
  section adds Slices 7 and 8.
- docs/DEV.md gets a Slice 8 — shipped section; the "Next slice"
  footer becomes the v1-complete epitaph.
- SPEC corrections per the §19.3 working agreement: §10.7 names the
  shared §12 sweep; §12 names the bot as actuator and the per-user
  branch_chat_seen preservation contract; §19.1 marks v1 complete
  and records Slice 8; the five §19.2 candidates Slice 8 folded in
  are marked settled with pointers at the resolution.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/tests/test_hygiene_vertical.py

@@ -272,12 +272,31 @@ def test_branch_chat_seen_survives_branch_deletion(app_with_fake_gitea):
             """,
             (long_ago, long_ago),
         )
-        # Seed a per-user seen cursor against the doomed branch.
+        # Seed a chat thread + message on the doomed branch, then the
+        # per-user seen cursor pointing at the message. The FK on
+        # branch_chat_seen.last_seen_message_id requires a real
+        # thread_messages row.
+        cur = db.conn().execute(
+            """
+            INSERT INTO threads (rfc_slug, branch_name, anchor_kind, thread_kind, created_by)
+            VALUES ('ohm', 'doomed', 'whole-doc', 'chat', 2)
+            """
+        )
+        thread_id = cur.lastrowid
+        cur = db.conn().execute(
+            """
+            INSERT INTO thread_messages (thread_id, role, author_user_id, text)
+            VALUES (?, 'user', 2, 'witness this')
+            """,
+            (thread_id,),
+        )
+        message_id = cur.lastrowid
         db.conn().execute(
             """
             INSERT INTO branch_chat_seen (user_id, rfc_slug, branch_name, last_seen_message_id, seen_at)
-            VALUES (2, 'ohm', 'doomed', 999, datetime('now'))
-            """
+            VALUES (2, 'ohm', 'doomed', ?, datetime('now'))
+            """,
+            (message_id,),
         )
 
         _aiorun(hygiene.run_tick(config=app.state.config, bot=app.state.bot))
@@ -292,7 +311,12 @@ def test_branch_chat_seen_survives_branch_deletion(app_with_fake_gitea):
             "SELECT last_seen_message_id FROM branch_chat_seen WHERE user_id = 2 AND branch_name = 'doomed'"
         ).fetchone()
         assert seen is not None
-        assert seen["last_seen_message_id"] == 999
+        assert seen["last_seen_message_id"] == message_id
+        # And the chat message itself survives — app-canonical, not cached.
+        msg = db.conn().execute(
+            "SELECT text FROM thread_messages WHERE id = ?", (message_id,)
+        ).fetchone()
+        assert msg["text"] == "witness this"
 
 
 def test_hygiene_action_kinds_fire_no_notifications(app_with_fake_gitea):