Document plans index in CLAUDE.md and plans/README.md

- Add plans/ to directory structure
- Add plans/index.json to shared state files table
- Add Plans row to component formats table
- Create plans/README.md with schema and query examples

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

plans/README.md

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+# Plans
+
+Implementation plans for features, enhancements, and investigations.
+
+## Structure
+
+```
+plans/
+├── index.json              # Status registry (source of truth)
+├── README.md               # This file
+└── *.md                    # Individual plan files
+```
+
+## Plan Naming
+
+- **Dated plans**: `YYYY-MM-DD-descriptive-name.md` (design docs)
+- **Generated names**: `adjective-verb-scientist.md` (brainstorming outputs)
+
+## Status Registry (index.json)
+
+Central tracking for all plans:
+
+```json
+{
+  "plan-name": {
+    "title": "Human readable title",
+    "status": "pending|implemented|partial|abandoned|superseded",
+    "created": "YYYY-MM-DD",
+    "implemented": "YYYY-MM-DD",
+    "category": "feature|enhancement|bugfix|diagnostic|design",
+    "notes": "Optional notes"
+  }
+}
+```
+
+### Status Values
+
+| Status | Meaning |
+|--------|---------|
+| `pending` | Not yet implemented |
+| `implemented` | Fully implemented |
+| `partial` | Partially implemented |
+| `abandoned` | Decided not to implement |
+| `superseded` | Replaced by another plan |
+
+### Categories
+
+| Category | Meaning |
+|----------|---------|
+| `feature` | New capability |
+| `enhancement` | Improve existing feature |
+| `bugfix` | Fix an issue |
+| `diagnostic` | One-time investigation |
+| `design` | Design document for reference |
+
+## Querying Plans
+
+```bash
+# List pending plans
+jq -r '.plans | to_entries[] | select(.value.status == "pending") | .key' index.json
+
+# List by category
+jq '.plans | to_entries[] | select(.value.category == "feature")' index.json
+
+# Count by status
+jq '.plans | to_entries | group_by(.value.status) | map({status: .[0].value.status, count: length})' index.json
+```
+
+## Workflow
+
+1. **Create plan**: Write `plans/plan-name.md`
+2. **Register**: Add entry to `index.json` with `status: "pending"`
+3. **Implement**: Execute the plan
+4. **Update**: Set `status: "implemented"` and add `implemented` date