Fix AMPA start-work failure: CONTAINER_PROJECT_ROOT undefined

[SorraTheOrc]

While running automated review for PR #1320, wl ampa start-work WL-0MNGQZC0V008GBUA failed with ReferenceError: CONTAINER_PROJECT_ROOT is not defined in ~/.config/opencode/.worklog/plugins/ampa.mjs:1794. This blocks isolated review execution (checkout, audit, code_review, tests) and prevents deterministic PR review flow.

Acceptance criteria:

1. wl ampa start-work succeeds without ReferenceError.
2. Container is correctly claimed and project workspace initialized.
3. wl ampa list-containers --json returns parseable entries with correct name/workItemId/status fields.
4. A rerun of PR Fix 51 failing tests: audit validation, GitHub async mocks #1320 review can complete audit/code review/test steps in-container.