fix(tools/fossil): address the requested changes in review feedback of Fossil SCM integration

[onlyarnav]

Summary

Addresses follow-up review feedback on the merged Fossil SCM integration (#736):

• Parser Unit Tests: Added unit tests in tools/vcs/tests/test_vcs.py to cover FossilBackend.status and FossilBackend.log timeline output parsing.
• CLI Argument Hardening: Added the -- separator before field name/value inputs in ticket commands to prevent options confusion.
• Resource Leaks: Wrapped SQLite connections using contextlib.closing to ensure handles are closed on exceptions.
• Safety warning: Swapped bare except Exception: pass catches with warning prints to stderr.

[potiuk]

Approving — this cleanly addresses the four review-feedback items on the Fossil integration:

• SQLite connection-leak fix via contextlib.closing(...) in find_repo_db / query_db — connections now close on the exception path too (parameterized queries preserved).
• Tighter exception handling in ticket.py: except Exception → except FossilError, warning to stderr instead of a silent pass.
• -- options-terminator hardening (with -R moved before --) — the right defensive pattern for the ticket add/set arg vectors.
• Good added test coverage for the vcs status/log parser (EDITED/ADDED/DELETED→M/A/D, extras→?, the VCSError→empty-status path, timeline + grep, bracket-in-comment case).

No credential/URL/injection surface introduced — list-form subprocess.run (no shell), clean_env(), parameterized SQL, DB-sourced artifact UUIDs. SPDX headers present.

One non-blocking follow-up worth a quick manual check: the -- hardening assumes Fossil's own arg parser honors -- in ticket add/set; the tests are mocked, so that isn't exercised against a real fossil binary. Thanks @onlyarnav.

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[potiuk]

I pushed a small follow-up (rebased on latest main): the three nested mock_run closures in tools/vcs/tests/test_vcs.py were missing type annotations, which workspace-mypy rejects (no-untyped-def) — annotated them as (args: list[str], cwd: str | None = None, **kwargs: object) -> str. mypy/ruff/pytest for tools/vcs pass locally and CI is now green. Merging. Thanks @onlyarnav.