feat(16-03): add revision_mode section to gsd-planner

- 6-step revision process for handling checker feedback
- Strategy table mapping issue dimensions to revision actions
- Surgeon mindset: minimal targeted updates to existing plans
- Return format for revision summary

agents/gsd-planner.md

@@ -837,6 +837,111 @@ gap_closure: true     # Flag for tracking
 
 </gap_closure_mode>
 
+<revision_mode>
+
+## Planning from Checker Feedback
+
+Triggered when orchestrator provides `<revision_context>` with checker issues. You are NOT starting fresh — you are making targeted updates to existing plans.
+
+**Mindset:** Surgeon, not architect. Minimal changes to address specific issues.
+
+### Step 1: Load Existing Plans
+
+Read all PLAN.md files in the phase directory:
+
+```bash
+cat .planning/phases/${PHASE}-*/*-PLAN.md
+```
+
+Build mental model of:
+- Current plan structure (wave assignments, dependencies)
+- Existing tasks (what's already planned)
+- must_haves (goal-backward criteria)
+
+### Step 2: Parse Checker Issues
+
+Issues come in structured format:
+
+```yaml
+issues:
+  - plan: "16-01"
+    dimension: "task_completeness"
+    severity: "blocker"
+    description: "Task 2 missing <verify> element"
+    fix_hint: "Add verification command for build output"
+```
+
+Group issues by:
+- Plan (which PLAN.md needs updating)
+- Dimension (what type of issue)
+- Severity (blocker vs warning)
+
+### Step 3: Determine Revision Strategy
+
+**For each issue type:**
+
+| Dimension | Revision Strategy |
+|-----------|-------------------|
+| requirement_coverage | Add task(s) to cover missing requirement |
+| task_completeness | Add missing elements to existing task |
+| dependency_correctness | Fix depends_on array, recompute waves |
+| key_links_planned | Add wiring task or update action to include wiring |
+| scope_sanity | Split plan into multiple smaller plans |
+| must_haves_derivation | Derive and add must_haves to frontmatter |
+
+### Step 4: Make Targeted Updates
+
+**DO:**
+- Edit specific sections that checker flagged
+- Preserve working parts of plans
+- Update wave numbers if dependencies change
+- Keep changes minimal and focused
+
+**DO NOT:**
+- Rewrite entire plans for minor issues
+- Change task structure if only missing elements
+- Add unnecessary tasks beyond what checker requested
+- Break existing working plans
+
+### Step 5: Validate Changes
+
+After making edits, self-check:
+- [ ] All flagged issues addressed
+- [ ] No new issues introduced
+- [ ] Wave numbers still valid
+- [ ] Dependencies still correct
+- [ ] Files on disk updated (use Write tool)
+
+### Step 6: Return Revision Summary
+
+```markdown
+## REVISION COMPLETE
+
+**Issues addressed:** {N}/{M}
+
+### Changes Made
+
+| Plan | Change | Issue Addressed |
+|------|--------|-----------------|
+| 16-01 | Added <verify> to Task 2 | task_completeness |
+| 16-02 | Added logout task | requirement_coverage (AUTH-02) |
+
+### Files Updated
+
+- .planning/phases/16-xxx/16-01-PLAN.md
+- .planning/phases/16-xxx/16-02-PLAN.md
+
+{If any issues NOT addressed:}
+
+### Unaddressed Issues
+
+| Issue | Reason |
+|-------|--------|
+| {issue} | {why not addressed - needs user input} |
+```
+
+</revision_mode>
+
 <execution_flow>
 
 <step name="load_project_state" priority="first">