refactor: Migrate from Claude Code to Codex CLI - .claude to .codex restructure

- Replaced .claude/ with .codex/ directory structure
- Created CODEX.md as root instructions for Codex
- Added .codex/prompts/ with templates for each development phase
- Added .codex/config/project.md for project configuration
- Removed .claude/agents/ (not compatible with Codex)
- Updated features/INDEX.md and docs/PRD.md references

.codex/config/project.md

@@ -0,0 +1,32 @@
+# Codex Configuration
+
+## Project Settings
+
+This project is optimized for Codex CLI autonomous coding.
+
+## Key Files
+
+- CODEX.md - Root instructions (this file guides Codex)
+- .codex/prompts/ - Pre-built prompts for each development phase
+- features/INDEX.md - Feature tracking and status
+- docs/PRD.md - Product Requirements Document
+
+## Development Workflow
+
+1. Requirements → 2. Architecture → 3. Frontend → 4. Backend → 5. QA → 6. Deploy
+
+Each phase uses `codex exec` with natural language prompts.
+See CODEX.md for example commands.
+
+## Conventions
+
+- Feature IDs: PROJ-1, PROJ-2, etc.
+- Commits: feat(PROJ-X): description
+- Tests: co-located with source files
+- shadcn/ui first: never recreate installed components
+
+## Recommended Flags
+
+- `--full-auto` for feature development (auto-approves changes)
+- `--yolo` for quick refactoring (no sandbox)
+- Interactive (default) for review/debugging

.codex/prompts/architecture.md

@@ -0,0 +1,16 @@
+# Architecture Prompt Template
+
+Use this prompt structure with Codex:
+
+```
+Read the feature spec at features/PROJ-X-feature-name.md.
+
+Design the technical architecture and add a "Tech Design" section to the spec with:
+- Component hierarchy (list components to build)
+- API endpoints (method, path, request/response shapes)
+- Database schema changes (tables, columns, RLS policies)
+- Implementation order (what to build first, dependencies)
+- Tech stack decisions ( libraries, patterns)
+
+Focus on: practical, implementable, PM-friendly (no code yet).
+```

.codex/prompts/backend.md

@@ -0,0 +1,19 @@
+# Backend Prompt Template
+
+Use this prompt structure with Codex:
+
+```
+Read the feature spec Tech Design section at features/PROJ-X-feature-name.md.
+Check existing APIs: ls src/app/api/
+Check Supabase schema: cat src/lib/supabase.ts
+
+[Describe what to build]
+
+Implementation rules:
+- Use Supabase client from src/lib/supabase.ts
+- Create API routes in src/app/api/[entity]/
+- Follow existing patterns for route structure
+- Add RLS policies for new tables
+- Write tests for all endpoints
+- Run: npm test after implementation
+```

.codex/prompts/deploy.md

@@ -0,0 +1,15 @@
+# Deploy Prompt Template
+
+Use this prompt structure with Codex:
+
+```
+Deploy to production:
+1. Run: npm run build (must succeed)
+2. Run: npm run lint (no errors)
+3. Run: vercel --prod
+4. Verify deployment URL
+5. Run smoke tests on production
+
+If build fails: fix errors first, then deploy.
+If lint errors: run npm run lint:fix, commit, then deploy.
+```

.codex/prompts/frontend.md

@@ -0,0 +1,21 @@
+# Frontend Prompt Template
+
+Use this prompt structure with Codex:
+
+```
+Read features/INDEX.md and the feature spec at features/PROJ-X-feature-name.md.
+Check existing components: ls src/components/ui/
+Check installed shadcn: ls src/components/ui/ | wc -l
+
+[Describe what to build]
+
+Implementation rules:
+- ALWAYS use shadcn/ui components (check src/components/ui/ first)
+- If missing: npx shadcn@latest add <component-name>
+- Tailwind CSS for all styling
+- Write unit tests next to source files (*.test.ts next to *.ts)
+- Run npm run lint after changes
+
+If design files exist: check design/ mockups/ assets/
+Otherwise ask about: visual style, brand colors, layout preference.
+```

.codex/prompts/qa.md

@@ -0,0 +1,20 @@
+# QA Prompt Template
+
+Use this prompt structure with Codex:
+
+```
+Read the feature spec at features/PROJ-X-feature-name.md, especially:
+- Acceptance criteria
+- User stories
+- Edge cases
+
+Test the implementation:
+1. Run unit tests: npm test
+2. Run E2E tests: npm run test:e2e
+3. Manual testing if needed
+4. Check each acceptance criterion
+5. Verify edge cases are handled
+
+Report: what passed, what failed, what needs fixing.
+Fix all failures before declaring done.
+```

.codex/prompts/requirements.md

@@ -0,0 +1,25 @@
+# Requirements Prompt Template
+
+Use this prompt structure with Codex:
+
+```
+Read docs/PRD.md to understand the project vision and constraints.
+Read features/INDEX.md to see existing features and the next available PROJ-X ID.
+
+[Describe the feature idea clearly]
+
+Create a feature specification in features/PROJ-X-feature-name.md with:
+- Feature name and ID
+- User stories (3-5, with: As a [role], I want [action], so that [benefit])
+- Acceptance criteria (testable, specific)
+- Edge cases (error handling, edge inputs, boundary conditions)
+- Dependencies (other features required)
+- Implementation notes (optional)
+
+Update features/INDEX.md with the new feature status.
+```
+
+Example:
+```
+codex exec "Read docs/PRD.md and features/INDEX.md. Create a feature spec for user authentication with email/password login, including: user stories for login/logout, acceptance criteria for valid/invalid credentials, edge cases for locked accounts and rate limiting."
+```