fix(local): remove a run's workspace when the watchdog terminalizes it

[lkshrk]

Problem

In local mode every run gets {workspace_base}/automation-runs/{run_id}, extracts its tarball there and builds a uv environment in it. Nothing removed that directory when the run ended, for two reasons that compound:

• LocalAgentServerBackend.cleanup_after_verification only logged Local mode: skipping cleanup (persistent server) and returned.
• _should_cleanup_sandbox_after_terminal required run.sandbox_id, which a local run never has, so the watchdog's terminal-cleanup path never reached the backend either.

The reporter saw six runs leave 2.6 GB on a PVC-backed ~/.openhands (~520 MB each, because UV_CACHE_DIR was on another filesystem and uv could not hardlink).

Change

• LocalAgentServerBackend.cleanup_after_verification now deletes the run's workspace directory. The agent server itself is still left alone, as it is persistent and externally managed.
• The watchdog predicate (renamed _should_cleanup_after_terminal) asks the backend rather than the sandbox id: keep_alive is not True and (bool(run.sandbox_id) or backend.is_local_mode). Cloud behaviour is unchanged, and a keep_alive run — which is how a continue_conversation sandbox is held — is still excluded.
• The guarded deletion the retention purge already had moved to openhands/automation/utils/workspace.py, so both callers share one implementation: a linked runs root or run directory is refused, so is anything resolving outside the runs root, and a run id that is not a UUID never reaches rmtree. Nothing raises; failures are logged.

No new setting. The retention sweep added in #277 (AUTOMATION_WORKSPACE_RETENTION_SECONDS, default 7 days) already covers the runs the watchdog never terminalizes — completed by callback, cancelled, or crashed — and its docstring now says so. An operator who wants those reclaimed in hours rather than days can lower that value today; happy to change the default in a follow-up if you'd rather ship a shorter one.

Deliberately not deleting the workspace from complete_run: the SDK sends that callback from the workspace context manager's __exit__, so the run's own process and the bash chain's EXIT trap are still live in that directory. The retention sweep is the safe place for that case.

HUMAN:

Reproduced the leak on a self-hosted Agent Canvas 1.16.0 before the change: six finished runs left 2.6 GB under ~/.openhands/workspaces/automation-runs and nothing ever removed them. Ran the branch through the full unit suite and all linters locally (1630 passed, ruff and pyright clean, pre-commit hooks pass) and verified through the new tests that the guarded delete refuses traversal and symlinked roots.

Testing'

uv run pytest tests/ -v --ignore=tests/integration   # 1630 passed, 56 skipped
uv run ruff check .                                  # clean
uv run ruff format --check .                         # clean
uv run pyright                                       # 0 errors
pre-commit run --files <changed>                     # all hooks pass

New tests cover: cleanup removes only the target run's directory; a non-UUID run id leaves a sibling directory untouched; a missing directory does not raise; and the predicate for a local run with no sandbox id (cleans up), the same run with keep_alive (does not), and a cloud run with no sandbox id (unchanged).

Fixes #422

https://claude.ai/code/session_01CC1C6MQsjZHysGccmVg7Fz

[all-hands-bot]

👋 This PR needs a couple of things fixed before OpenHands can review it:

• the PR description's HUMAN: section needs at least 20 characters describing what you tested, not just the template placeholder

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