fix(agentos-sidecar): harden the close_session already-exited short-circuit

[NathanFlurry]

• Builds on fix(agentos-sidecar): skip close_session teardown wait when the adapter already exited #1640: also short-circuit on the session record already marked closed (covers exits the kill RPC does not report), and skip the second wait when SIGKILL itself reports the process gone.
• Mirror the short-circuit in the agentos-sidecar-core sync engine, with regression tests proving zero dead waits.

[NathanFlurry]

Stack for rivet-dev/agentos

• feat(runtime-core): replace the sidecar frame timeout with a heartbeat silence watchdog #1653 rwrqkykq · 2026-07-08 02:56:14
• fix(core): deliver post-boot mountFs reconfiguration reliably to the native sidecar #1660 nyvvsyxp · 2026-07-08 05:10:55
• fix(native-sidecar): resolve js_bridge mount-root realpath without a bridge round-trip #1659 wmqznzol · 2026-07-08 05:10:54
• fix(agentos-sidecar): harden the close_session already-exited short-circuit #1658 mkkuuouw · 2026-07-08 05:10:53 👈
• main

Get stack: forklift get 1658
Push local edits: forklift submit
Merge when ready: forklift merge 1658

[railway-app]

🚅 Deployed to the agentos-pr-1658 environment in agentos

Service	Status	Web	Updated (UTC)
agentos	😴 Sleeping (View Logs)	Web	Jul 8, 2026 at 5:23 am

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🚅 Environment agentos-pr-1658 in rivet-frontend has no services deployed.