merge: sync Rongsong's scheduler-framework into chatbot

Full merge of origin/scheduler-framework (scheduler-core restructure,
failover-adoption, WAL_JOB_DISPATCH, apiserver backend health/heartbeat,
build-time versioning, bug-1673/1676/1678/1679/1680).

Conflict resolution:
- scheduler: adopt Rongsong's scheduler-core architecture (driver loop,
  queue project/picker fields, resource bug-1569 fix)
- worker/controller_connector.c: keep Rongsong's reconnect/rejoin
  structure, PORT our bug-1509 resend_job_status onto the rejoin success
  path (his reconnect didn't re-report job state)
- apiserver backend: take Rongsong's health/heartbeat (supersedes our
  e505066 circuit breaker)
- group.c: keep our bug-1513 comment
- misc: take theirs for additive fixes (go_build versioning,
  test_group.c, persist.c RUSAGE_UPDATE, FilterRows bug-1680)

NOTE: our scheduler fixes (bug-1494 family dispatch-fail requeue,
PEND-reason classification) are NOT in Rongsong's branch — needs
verification/porting onto scheduler-core (separate follow-up).

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

CLAUDE.md

@@ -29,7 +29,7 @@ For details on any topic below, read the corresponding steering file in `.kiro/s
 ## Key Rules (from steering — summarized for quick reference)
 
 - **TDD mandatory**: red → green → refactor; test in `testsuite/` before C changes, `_test.go` before Go changes
-- **Async I/O**: never block in vtask handlers; delaymgr for blocking ops. `xce_request`/`xce_reply` are always non-blocking
+- **Async I/O**: delaymgr is trigger-only and must never block (no `connect()`, no file I/O) — it drives heartbeats/election timeouts, so blocking there causes spurious failover. Long/unbounded blocking goes on the slow lane; bounded blocking in vtask handlers is permitted only under an admission reservation (`COMMIT_WAIT_RESERVED`). `xce_request`/`xce_reply` are always non-blocking. See `ha-async-io.md`
 - **Connections are long-lived**: closing signals RDHUP failover. Inbound connections are vote-only; outbound carry all state push
 - **Middleware chain** (non-negotiable): WhitelistURL → WhitelistIP → RateLimit → JWT → CORS → RBAC
 - **Error pattern**: `ReturnError(code, msg, nil); return` — early return on every error
@@ -101,5 +101,5 @@ Kiro-style Spec-Driven Development on an agentic SDLC
 ## Steering Configuration
 - Load entire `.kiro/steering/` as project memory — all `.md` files are authoritative
 - Core: `product.md`, `tech.md`, `structure.md`
-- Custom: `testing.md`, `error-handling.md`, `security.md`, `ha-async-io.md`, `api-standards.md`, `build-deployment.md`
+- Custom: `testing.md`, `error-handling.md`, `security.md`, `ha-async-io.md`, `api-standards.md`, `build-deployment.md`, `config-design.md`, `persistence.md`, `roadmap.md`
 - Add new custom files via `/kiro-steering-custom`; sync existing via `/kiro-steering`