refactor(#1190): extract ADR-22 drift-guard decision logic into a testable seam (#1242)

* refactor(#1190): extract ADR-22 drift-guard decision logic into a testable seam

ADR-22's severity mapping, authority auto-upgrade, and rung>=3 hard-block lived only as prose in plan-review-convergence.md — untestable. Extracted into src/plan-drift-guard.cts (pure: AUTHORITY_RUNGS, getEffectiveAuthority, classifyDriftSeverity) + a gsd-tools drift-guard CLI seam (authority/severity), and rewired the workflow to call the seam deterministically instead of reasoning the decision in prose. 47 unit/e2e/structural tests cover the full severity table, the grep->intel auto-upgrade, and the rung>=3 HIGH hard-block.

Closes #1190

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* chore(#1190): add changeset for ADR-22 drift-guard seam (#1242)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix(#1190): register ADR-22 module in eslint-ignore + inventory manifest + docs-exempt changeset

Full-matrix CI surfaced new-module/command governance ripples beyond the lint-tests chain: (1) tsc-generated plan-drift-guard.cjs must be in the eslint ignore list (551-eslint-bin-lib-coverage); (2) docs/INVENTORY-MANIFEST.json must include the new module/command (regen via gen-inventory-manifest.cjs --write); (3) a type:Added changeset triggers docs-required — added a docs-exempt marker (internal seam, no user-facing surface).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

docs/INVENTORY-MANIFEST.json

@@ -336,6 +336,7 @@
       "phase-locator.cjs",
       "phase.cjs",
       "phases-command-router.cjs",
+      "plan-drift-guard.cjs",
       "plan-scan.cjs",
       "planning-workspace.cjs",
       "probe-core.cjs",