chore: configure GSD for maximum-rigor remediation

Settings chosen for the Mokosh stabilization work:
- model_profile: quality (Opus everywhere except verification)
- git.branching_strategy: phase (gsd/phase-{N}-{slug} per phase)
- workflow.code_review: true with depth=deep (cross-file analysis with
  import graphs — appropriate given the SW ↔ offscreen ↔ content-script
  messaging interplay)
- workflow.tdd_mode: true (RED/GREEN/REFACTOR gates for eligible tasks,
  retrofits regression coverage as we touch each file)

All other settings inherit gsd-sdk defaults (research/plan-check/verifier
on, balanced commit_docs, no Intel/Graphify indexing yet).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.planning/config.json

@@ -0,0 +1,11 @@
+{
+  "model_profile": "quality",
+  "git": {
+    "branching_strategy": "phase"
+  },
+  "workflow": {
+    "code_review": true,
+    "code_review_depth": "deep",
+    "tdd_mode": true
+  }
+}