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/main.py

@@ -212,6 +212,7 @@ async def queue():
     from . import fs_normalize
     from . import labels
     from . import cancel
+    from . import bug_fast_track
     from .disk_watchdog import disk_watchdog
     from .build_cache_pruner import build_cache_pruner
     return {
@@ -243,6 +244,10 @@ async def queue():
         # repo scope, cancelled/deferred counts, recent cancellations. Additive block;
         # never-raise.
         "stop": cancel.snapshot(),
+        # ORCH-019 (FR-7 / AC-7): bug-fast-track observability (read-only) —
+        # kill-switch, label, scope, bug-task counts + the structural savings metric
+        # (architecture stages skipped). Additive block; never-raise.
+        "bug_fast_track": bug_fast_track.snapshot(),
         # ORCH-063 (FR-6 / AC-7): disk-watchdog observability (read-only) —
         # enabled, threshold, interval, last measurement per host-path. Additive
         # block; never-raise (status() returns {"enabled": ...} minimum on error).
@@ -343,3 +348,45 @@ async def coverage_set_baseline(repo: str = "", value: float | None = None):
     repo = repo.strip()
     ok = db.set_coverage_baseline(repo, value, sha="manual-override")
     return {"ok": ok, "repo": repo, "baseline": db.get_coverage_baseline(repo)}
+
+
+@app.post("/bug-fast-track/escalate")
+async def bug_fast_track_escalate(work_item: str = ""):
+    """ORCH-019 (FR-5 / AC-5, ADR-001 D5): escalate a bug-fast-track task to the
+    full cycle (return it to the route WITH `architecture`).
+
+    Operator path for a bug that turned out to be complex / architectural / visual
+    (needs an ADR or a mock): reset ``tasks.track`` 'bug' -> 'full'. Apply while the
+    task is still in `analysis` (before its exit) — the next advance_stage then routes
+    analysis -> architecture normally. By образцу ``POST /serial-gate/unfreeze`` /
+    ``POST /coverage/baseline``. never-raise.
+    """
+    from . import db
+    if not work_item or not work_item.strip():
+        return {"ok": False, "error": "missing 'work_item'", "work_item": work_item}
+    work_item = work_item.strip()
+    task = db.get_task_by_work_item_id(work_item)
+    if not task:
+        return {"ok": False, "error": "unknown work_item", "work_item": work_item}
+    prev_track = task.get("track") or "full"
+    db.set_task_track(task["id"], "full")
+    if prev_track == "bug":
+        try:
+            from .notifications import send_telegram
+            send_telegram(
+                f"🐞➡️ {work_item}: эскалация в ПОЛНЫЙ цикл "
+                f"(багфикс-трек снят, стадия architecture восстановлена)."
+            )
+        except Exception:
+            pass
+        try:
+            from .plane_sync import add_comment
+            add_comment(
+                work_item,
+                "🐞➡️ Эскалация: задача возвращена в полный цикл "
+                "(багфикс-трек снят, стадия architecture восстановлена).",
+                author="analyst",
+            )
+        except Exception:
+            pass
+    return {"ok": True, "work_item": work_item, "track": "full", "was": prev_track}