feat(bug-fast-track): cheaper/shorter pipeline route for bug-fix tasks (ORCH-019)

A task carrying the Plane `Bug` label takes a shortened route that skips the
`architecture` stage (one opus architect run + ADR + check_architecture_done),
replacing heavy analysis with a lite package (bug-report + mandatory regression
test plan). EVERY Quality Gate / sub-gate runs UNCHANGED — the route is a
scheduler property, not a gate (root invariant NFR-1): STAGE_TRANSITIONS /
QG_CHECKS / check_* / machine-verdict keys are byte-for-byte preserved.

- src/bug_fast_track.py: new leaf (never-raise) — bug_fast_track_applies (local,
  network-free, checked first), is_bug_task (labels.has_label, Plane API source),
  skips_architecture (pure DB-backed routing predicate), snapshot.
- src/db.py: additive idempotent tasks.track column (TEXT DEFAULT 'full') +
  set_task_track / get_task_track helpers (missing/NULL -> 'full', fail-safe).
- src/stage_engine.py: routing-override on the analysis-exit edge (track='bug' ->
  development/developer, skipping architect); brd-review-clock stamp extended to
  analysis->development. get_next_stage/get_agent_for_stage stay pure.
- src/webhooks/plane.py: classify task as bug in start_pipeline (applies-first
  short-circuit; never-raise -> full cycle on any error).
- src/main.py: additive bug_fast_track block in GET /queue + POST
  /bug-fast-track/escalate (reset 'bug'->'full' to return to the full cycle).
- src/config.py: bug_fast_track_enabled / _label / _repos flags (empty CSV ->
  self-hosting only).
- src/notifications.py: optional 🐞 marker on the bug-track card (never-raise).
- Prompts: analyst.md (lite bug package + escalation), reviewer.md (regression-
  test axis) — 52d canon preserved.
- Docs: CLAUDE.md, README.md (env + API + section), docs/architecture/README.md,
  CHANGELOG.md, .env.example.
- Tests: tests/test_bug_fast_track*.py + test_db_migrations.py + queue block
  (TC-01..TC-15). Full regression green (1551 passed).

Kill-switch ORCH_BUG_FAST_TRACK_ENABLED=false -> 1:1 pre-ORCH-019 (zero
regression; residual track column harmless).

Refs: ORCH-019

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/notifications.py

@@ -452,10 +452,18 @@ def render_task_tracker(task_id: int) -> str:
     task_repo = _row_get(task, "repo")
     task_issue_id = _row_get(task, "plane_issue_id")
     num_html = plane_issue_link(work_item_id, plane_issue_id=task_issue_id, repo=task_repo)
+    # ORCH-019 (D7): mark a bug-fast-track task with a \ud83d\udc1e in the header. Optional,
+    # never-raise \u2014 any error simply omits the marker (the card always renders).
+    bug_marker = ""
+    try:
+        if (_row_get(task, "track") or "").strip().lower() == "bug":
+            bug_marker = "\U0001f41e "
+    except Exception:
+        bug_marker = ""
     header = (
-        f"\U0001f389 {num_html} \u00b7 {esc_title} \u2014 \u0413\u041e\u0422\u041e\u0412\u041e"
+        f"\U0001f389 {bug_marker}{num_html} \u00b7 {esc_title} \u2014 \u0413\u041e\u0422\u041e\u0412\u041e"
         if done
-        else f"\U0001f6e0\ufe0f {num_html} \u00b7 {esc_title}"
+        else f"\U0001f6e0\ufe0f {bug_marker}{num_html} \u00b7 {esc_title}"
     )
     bar = "\u2501" * 22
     # ORCH-067 (req 2): a Plane-status line (model ORCH-066) under the header.