feat(workflow): enforce fresh base branch and add local governance check

[yohnark]

Summary

Fix two of the four performance issues found in today's codex sessions (Issue #48, #25, mottainai config): stale base branches slipping past task start, and PR governance checks only surfacing after CI runs.

Linked issue

Closes #61

Scope

Included

• policy.worktree.staleBaseBranch policy flag (default off, enforce on strict-worktree, advisory on standard) plus checkStaleBaseBranch in startTask that rejects task starts when the local base branch trails origin/<branch>.
• scripts/governance-check-local.mjs (pnpm run governance:pr:local): runs the existing validatePullRequest and validateBranchName against local git state (title/body/diff/branch) before gh pr create, instead of only after CI.
• scripts/governance-check-issue-local.mjs (pnpm run governance:issue:local): local equivalent of validate-issue.mjs for checking a draft issue body before gh issue create. Added after this PR's own first two pushes failed CI on exactly the gaps these two commands close (non-compliant branch name, then a missing "Implementation notes" section on the linked issue) — see PR discussion.

Excluded

• architecture:check local/CI unification — already solved on PR feat(ci): enforce coding standards and architecture boundaries #59 via verify:standards, no change needed here.
• Worktree bootstrap MCP config copying — investigated and found unnecessary; Mottainai MCP registration lives in the global ~/.codex/config.toml, not per-worktree, and the actual failure (unresolved global bin) was already fixed in a separate session.

Implementation

• checkStaleBaseBranch compares local baseCommit against origin/<baseBranch> via git merge-base --is-ancestor; only rejects when local is a strict ancestor of the remote tip (avoids false positives on diverged/ahead branches). No implicit git fetch — it only checks what's already known locally.
• governance-check-local.mjs reuses validatePullRequest and validateBranchName from governance-lib.mjs unchanged; only the input-resolution layer (title from --title or last commit subject, body from --body-file or last commit body, files from --files or git diff --name-only, branch from --branch or git branch --show-current) is new.
• governance-check-issue-local.mjs reuses validateIssue from governance-lib.mjs unchanged; same input-resolution pattern via --body-file/--body.

Behavioral changes

• Task start can now fail with unsupported-repo-state when staleBaseBranch=enforce and the local branch is behind origin. Only affects strict-worktree preset by default; existing standard/minimal presets are unaffected (advisory/off).
• New optional local commands pnpm run governance:pr:local and pnpm run governance:issue:local; no change to existing governance:pr/governance:issue (CI) behavior.

Validation

• Typecheck
• Tests
• Build
• Package check

Risks

• staleBaseBranch check relies on the local repo already having an up-to-date origin/<branch> ref; it does not fetch, so a caller who never fetches gets no protection (documented in code comment). Low risk since it's opt-in via policy and defaults to off.

Breaking changes

No.

Review focus

• Whether strict-worktree defaulting staleBaseBranch to enforce is the right call, or if it should start at advisory for a rollout period.

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Run ID: 3b16326c-0803-4831-bfd5-0e03040586e6

📥 Commits

Reviewing files that changed from the base of the PR and between 273b324 and ef38660.

📒 Files selected for processing (9)

• package.json
• scripts/governance-check-issue-local.mjs
• scripts/governance-check-issue-local.test.mjs
• scripts/governance-check-local.mjs
• scripts/governance-check-local.test.mjs
• src/workflow/domain/task.test.ts
• src/workflow/domain/task.ts
• src/workflow/policy/presets.ts
• src/workflow/policy/schema.ts

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