docs(#22): add ADR for plan-vs-codebase drift guard (defaults + resolver seam) (#484)

Consolidated decision record: source-grounding verification default-on
(plan_review.source_grounding), intel.enabled stays opt-in, and the
three-valued symbol-resolver seam with a climbable adapter ladder.

Refs #22

Co-authored-by: CI Rebase Check <ci@gsd-redux>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/adr/README.md

@@ -46,6 +46,7 @@ See **[CONTRIBUTING.md — "Proposing an ADR or PRD"](../../CONTRIBUTING.md#prop
 | [0011-review-default-reviewers-prd.md](0011-review-default-reviewers-prd.md) | PRD for review.default_reviewers feature (#3464) | Reference |
 | [0012-command-routing-hub.md](0012-command-routing-hub.md) | CommandRoutingHub as single dispatch seam for CJS command families | Superseded by ADR-0174 |
 | [15-autonomous-cross-ai-convergence.md](15-autonomous-cross-ai-convergence.md) | Cross-AI plan convergence via existing orchestration commands | Proposed |
+| [22-plan-drift-guard.md](22-plan-drift-guard.md) | Plan-vs-codebase drift guard: defaults and symbol-resolver seam | Proposed |
 | [3524-cjs-sdk-hard-seam.md](3524-cjs-sdk-hard-seam.md) | CJS↔SDK hard seam — single canonical owner per responsibility (#3524) | Superseded by ADR-0174 |
 | [3660-runtime-artifact-layout-module.md](3660-runtime-artifact-layout-module.md) | Runtime Artifact Layout Module owns per-runtime artifact placement | Proposed |
 | [0174-retire-gsd-sdk-package-boundary.md](0174-retire-gsd-sdk-package-boundary.md) | Retire @opengsd/gsd-sdk package boundary — single-runtime collapse | Accepted |