Persist verified task completion before advancing - #81

Discussion Link

Link: No linked discussion. Work is tracked by #56.

Context

Agents can lose implementation progress and repeat completed work when completion records are not persisted, especially before a commit or PR exists.

Closes #56

Solution

Require durable completion evidence and readback before advancing or committing. Inspect evidence before resume state changes, preserve verified local checkboxes, and use actual supported Azure DevOps states. Execution workers return evidence and pending commit scopes. The coordinator owns commits after verification and checkpoint persistence, including normal, streamlined, deferred-commit, and drift paths. Keep final closure merge-driven.

Stack dependency: #80. Merge that PR first, then retarget this PR to main if GitHub has not retargeted it automatically. This PR targets feature/39-pipeline-protection so its diff contains only this issue's changes.

Validation

• npm --prefix docs run build: passed in an isolated snapshot of this PR's committed tree (39 pages).
• node --check docs/astro.config.mjs: passed.
• git diff feature/39-pipeline-protection feature/56-durable-task-completion --check: passed.
• markdownlint --stdin --json --config .markdownlint.yaml: no new diagnostics versus the base across 8 changed Markdown/MDX files. Existing diagnostics are unchanged.
• Independent instruction review completed. No test board items or live branch-protection settings were changed.

Checklist

• Linked discussion exists
• Solution has been validated