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>
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