perf(hooks): tighten STDIN timeout, add try-catch, move pull to background

[m0Nst3r873]

Summary

Three independent hook dispatch optimizations to improve reliability and responsiveness:

• STDIN timeout 2s → 1s: Healthy hosts EOF within milliseconds; the 2s timeout was overly generous for the missing-EOF edge case
• Top-level try-catch in hookDispatchCli: Prevents unexpected errors (dynamic import failures, config parse errors) from crashing the hook process — logs at warn level for diagnosability
• pullHandler moved to background on session-start: pull does not produce output the host needs to inject, so running it detached avoids blocking session startup on slow git fetches

Changes

• src/hook-dispatch-cli.ts: Reduce STDIN_READ_TIMEOUT_MS from 2000 to 1000; wrap hookDispatchCli body in try-catch with log.warn
• src/hook-handlers.ts: Change pullHandler registration from foreground to background: true with LOCAL_AGENT_TIMEOUT_MS

Test plan

• npx tsc --noEmit — type check passes
• npx vitest run — 1885 tests pass (143 files), including golden tests
• npm run build — build succeeds
• Trigger session-start hook, verify pull runs in background (not blocking session prompt)
• Simulate hookDispatchCli error, verify warn-level log appears in stderr

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