/crumb-debug — F1-F7 routing fault diagnosis
When the user reports the session is stuck / broken:
Preferred path — call the crumb_debug MCP tool with {session: "<ulid>"}.
Fallback path — npx tsx src/index.ts debug <session-id>.
If all clear, the report says ✅ No faults detected. Otherwise table of detected F1-F7 with evidence + suggested action.
Explicit slash form: /crumb-debug <session-id>.
Reference: src/helpers/debug.ts, v0.1 §8.2 (F1-F7 fault matrix), wiki/concepts/bagelcode-fault-tolerance-design.md.