docs: Add Session Scratchpad design and update project references

- Add Session Scratchpad design doc (Idea 6 from brainstorm)
- Update CLAUDE.md production URLs to resolutionflow.com
- Update CORS lesson domain refs for rebrand
- Add .claude/settings.local.json to gitignore docs
- Add docs/plans/ to project structure

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

CLAUDE.md

@@ -24,7 +24,7 @@ The project was rebranded from "Patherly" to "ResolutionFlow" in the frontend (P
 | Repository / directory name | `patherly` |
 | Backend (FastAPI, env vars, APP_NAME) | ResolutionFlow |
 | Database / Docker container | `patherly` / `patherly_postgres` |
-| Production URLs | `app.patherly.com` / `api.patherly.com` |
+| Production URLs | `resolutionflow.com` / `api.resolutionflow.com` |
 | **Frontend UI (header, login, register)** | **ResolutionFlow** |
 | **Browser tab title** | **ResolutionFlow - Decision Tree Platform** |
 
@@ -216,6 +216,7 @@ patherly/
 ├── LESSONS-LEARNED.md              # Bugs and fixes (READ THIS!)
 ├── PROGRESS.md                     # Detailed progress log
 ├── REBRAND-IMPLEMENTATION-GUIDE.md # Patherly → ResolutionFlow rebrand guide
+├── docs/plans/                     # Implementation plans
 ├── 01-PROJECT-OVERVIEW.md          # Vision and goals
 ├── 02-TECHNICAL-ARCHITECTURE.md    # System design, API specs
 ├── 03-DEVELOPMENT-ROADMAP.md       # Phases and timeline
@@ -468,12 +469,12 @@ if settings.ALLOW_RAILWAY_ORIGINS:
 if settings.ALLOW_RAILWAY_ORIGINS:
     app.add_middleware(
         CORSMiddleware,
-        allow_origins=settings.allowed_origins,  # Custom domains like app.patherly.com
+        allow_origins=settings.allowed_origins,  # Custom domains like resolutionflow.com
         allow_origin_regex=r"https://.*\.up\.railway\.app",  # Railway PR domains
         # ...
     )
 ```
-When using `allow_origin_regex` for wildcard patterns, also include `allow_origins` for explicit custom domains. The regex alone won't match custom domains like `app.patherly.com`.
+When using `allow_origin_regex` for wildcard patterns, also include `allow_origins` for explicit custom domains. The regex alone won't match custom domains like `resolutionflow.com`.
 
 ### findNode Requires Tree Structure Parameter
 
@@ -738,6 +739,7 @@ const response = await api.get('/api/v1/trees')
 # Secrets and local config
 backend/.env
 .claude.local.md
+.claude/settings.local.json
 
 # Dependencies
 backend/venv/
@@ -778,8 +780,8 @@ backend/**/__pycache__/
 
 ### Production
 
-- **Frontend:** https://app.patherly.com
-- **Backend:** https://api.patherly.com
+- **Frontend:** <https://resolutionflow.com>
+- **Backend:** <https://api.resolutionflow.com>
 - **Database:** Railway-managed PostgreSQL
 - Deploys automatically on push to `main`