fix(daemon): acknowledge checkpoint admission asynchronously

[svarlamov]

Summary

• acknowledge CheckpointRun after ordered family admission instead of side-effect completion
• retain sync.family as the processing completion and error boundary
• make health probes active and defer automatic restart paths while admitted checkpoints remain
• add admission, queue, execution, and trace-progress diagnostics without adding work to trace ingress
• honor the checkpoint-captured base during delayed processing instead of falling back to mutable HEAD

Tests

• delayed checkpoint admission, Ping responsiveness, sync completion, and exact post-commit attribution
• admission versus processing error interface coverage
• cross-family checkpoint isolation and watchdog coverage
• full task test, task lint, task fmt, and task build

Depends on #1981.

[svarlamov]

Warning

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Learn more

• fix(daemon): acknowledge checkpoint admission asynchronously #1982 👈 (View in Graphite)
• fix(daemon): decouple trace ingestion from side effects #1981
• refactor(daemon): add bounded family drain scheduling #1980
• fix(daemon): suppress unnecessary agent checkpoint traffic #1979
• main

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