fix(core): reap worktrees for terminated sessions

[ChiragArora31]

Problem

ao session cleanup could report already-terminated sessions as handled while leaving their managed worktrees on disk. This happens when lifecycle metadata reaches terminated through paths such as runtime_lost or a previous interrupted kill before workspace cleanup ran.

Closes #1524.

What changed

• Allows kill() to safely retry workspace-only cleanup for sessions whose lifecycle is already terminal.
• Keeps runtime and agent teardown idempotent for already-terminated sessions.
• Makes cleanup() report already-terminated sessions as cleaned only when it actually reaps a remaining managed worktree or OpenCode mapping.
• Adds regression tests for direct kill, cleanup, and repeated cleanup idempotency.

Validation

• pnpm --filter @aoagents/ao-core test -- src/__tests__/session-manager/lifecycle.test.ts
• pnpm --filter @aoagents/ao-core typecheck
• pnpm --filter @aoagents/ao-core build && pnpm --filter @aoagents/ao-plugin-tracker-github build && pnpm --filter @aoagents/ao-plugin-scm-github build
• pnpm --filter @aoagents/ao-core test

Checklist

• Tests added/updated
• No breaking changes

[greptile-apps]

Greptile Summary

This PR fixes a resource-leak bug where managed worktrees could be left on disk after a session's lifecycle was already marked terminated (e.g., via runtime_lost or a previously interrupted kill). The fix allows kill() to perform a safe, workspace-only cleanup retry when a session is already terminal, and wires the cleanup loop to report those sessions as killed rather than skipped.

• Extracts destroyManagedWorkspace() and hasReapableManagedWorkspace() helpers to deduplicate workspace-destruction logic across kill() and cleanup().
• Updates the terminated-session fast-path in kill() to attempt workspace reap (with requireExisting: true) before returning { cleaned, alreadyTerminated: true }.
• Updates the cleanup() second loop to call kill() for terminated sessions and use cleanedTerminatedWorkspace to decide killed vs skipped, covering both standalone-worktree and OpenCode-agent sessions.

Confidence Score: 5/5

Safe to merge; changes are narrowly scoped to workspace-only cleanup for already-terminated sessions, with no new side effects on live sessions.

The fix correctly adds requireExisting: true to the terminated fast-path to avoid spurious destroy calls, invalidates the cache only when a workspace was actually reaped, and keeps runtime/agent teardown skipped for already-terminated sessions. Three targeted regression tests cover the new paths including idempotency on double-cleanup.

No files require special attention.

Important Files Changed

Filename	Overview
packages/core/src/session-manager.ts	Core fix: adds destroyManagedWorkspace/hasReapableManagedWorkspace helpers and updates kill() terminated fast-path and cleanup() second loop to reap orphaned worktrees; logic is correct and idempotent.
packages/core/src/tests/session-manager/lifecycle.test.ts	Adds three regression tests covering direct kill, cleanup reap, and idempotent double-cleanup for already-terminated sessions; mock isolation is correct via beforeEach/afterEach.
packages/core/src/types.ts	Updates KillResult JSDoc to accurately reflect that cleaned and alreadyTerminated can both be true simultaneously.
.changeset/reap-terminated-session-worktrees.md	Adds a patch-level changeset entry for @aoagents/ao-core describing the fix.

_{Reviews (2): Last reviewed commit: "Merge remote-tracking branch 'upstream/m..." | Re-trigger Greptile}

[ChiragArora31]

Rechecked this after the earlier lint failure: the current PR checks are green, including Lint. I also rebuilt locally before running tests so stale dist output does not affect validation.