fix: retain timed-out bash commands and clean up shells on runtime exit

[frostming]

Foreground bash commands that exceed timeout_seconds now continue in the background and return a shell_id, instead of being terminated. Output remains available through bash.output, and bash.kill can stop the command. Explicit background responses also include the shell ID and follow-up actions.

Shell ownership now follows the runtime lifecycle:

• A new provide_lifespan hook enters plugin resource generators within framework.running(). The builtin implementation owns shells across turns and cleans them up on normal exit, exceptions, cancellation, and startup failure.
• Separate runtime scopes remain independent, including when they use the same session ID. Shutdown waits for in-flight process creation, and tasks cannot create shells after their owning scope closes.
• On POSIX, foreground completion cleans up remaining process-group members even if the shell leader has exited and its children redirected their output.
• Termination finishes before cancellation propagates, including repeated cancellation. Cleanup continues for other shells if one reader fails. Timeout during cleanup does not return a released shell ID.

Tests cover continued output after timeout, explicit termination, session and runtime cleanup, scope isolation, spawn/shutdown races, repeated cancellation, and descendant termination. English and Chinese hook documentation describe the lifecycle and its limits.

Limits: cleanup covers the POSIX process group. Descendants that deliberately leave it and abrupt SIGKILL of Bub require OS-level supervision. Windows currently terminates only the direct shell process. SDK callers need to run the builtin lifecycle within framework.running() (or explicitly manage their ShellManager lifespan).

Validation:

• Full pytest suite with doctests: 485 passed, 1 skipped.
• Ruff checks and formatting passed.
• mypy passed for all 51 source files.
• Website/docs production build passed.
• git diff --check passed.

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	bub	2f6f19a	Commit Preview URL Branch Preview URL	Sep 21 2026, 01:58 AM