Add cross-tool workflow: AGENTS.md, Antigravity workflows, documentation

- Create AGENTS.md (90 lines) as shared foundation for Claude Code + Antigravity
- Slim CLAUDE.md from 113 to 45 lines (Claude-specific only, references AGENTS.md)
- Slim GEMINI.md from 58 to 26 lines (Antigravity-specific only, references AGENTS.md)
- Add 6 Antigravity workflows in .agent/workflows/ (session-start, preflight, token-sync, visual-qa, build-component, page-review)
- Add docs/reference/cross-tool-workflow.md with task routing, quality gates, file ownership, error mitigation
- Zero content overlap between CLAUDE.md and GEMINI.md (was ~80%)
- File ownership boundaries defined for current phase and future backend work

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

AGENTS.md

@@ -0,0 +1,90 @@
+# FA 2.0 Design System
+
+## Project
+
+Funeral Arranger (funeralarranger.com.au) design system rebuild. Client: Parsons
+(H.Parsons Funeral Directors). Users are often in distress — the design language
+must be warm, professional, trustworthy, and calm.
+
+## Tech stack
+
+- React 18 + TypeScript
+- Material UI (MUI) v5
+- Storybook 8+ with autodocs
+- Style Dictionary for token transformation
+- W3C DTCG token format (2025.10 stable spec)
+
+## Architecture
+
+Source of truth: token JSON files in `tokens/` (DTCG format).
+Flow: Token JSON → Style Dictionary → MUI theme + CSS vars → React components → Storybook
+
+Token tiers: primitives (`tokens/primitives/`) → semantic (`tokens/semantic/`) → component (`tokens/component/`)
+Component tiers: atoms → molecules → organisms → templates → pages (in `src/components/`)
+
+## Commands
+
+- `npm run build:tokens` — regenerate CSS/JS from token JSON (run after any token change)
+- `npm run storybook` — dev server on localhost:6006
+- `npm run type-check` — TypeScript compilation check
+- `npm run lint` / `npm run lint:fix` — ESLint
+- `npm run format` / `npm run format:check` — Prettier
+- `npm run test` — Vitest
+
+## Rules (always)
+
+1. Consume the MUI theme for all visual values — `theme.palette.*`, `theme.spacing()`, `theme.typography.*`
+2. Every token has `$value`, `$type`, and `$description` (DTCG format)
+3. Error styling uses copper (#B0610F) not red — grief-sensitive context
+4. Read `docs/memory/` before starting work (decisions-log, component-registry, token-registry, session-log)
+5. Update `docs/memory/` after completing work
+6. Run `npm run build:tokens` after any token JSON change
+7. Verify in Storybook before marking any component done
+8. Follow the component lifecycle in `docs/reference/component-lifecycle.md`
+9. Commit and push after each coherent unit of work
+
+## Rules (never)
+
+- Use raw hex values in component source files — map to semantic tokens
+- Mix token access methods — semantic via `theme.*`, component via `var(--fa-*)`
+- Skip the barrel export (`index.ts`) for any component
+- Edit files owned by another agent without coordinating (see File ownership)
+
+## Git workflow
+
+Remote: Gitea at `http://192.168.50.211:3000/richie/ParsonsFA.git`
+Branch: all work on `main` for now.
+
+Stage specific files (not `git add -A`). Commit message format:
+```
+Short summary (imperative mood, <70 chars)
+
+- Bullet points with detail if needed
+- Reference decision IDs (D001, D002...) when relevant
+```
+
+## File conventions
+
+- Component folders: PascalCase — `Button/`, `PriceCard/`
+- Token files: camelCase — `colours.json`, `typography.json`
+- Each component folder: `ComponentName.tsx`, `ComponentName.stories.tsx`, `index.ts`
+- CSS custom properties prefix: `--fa-`
+- Semantic tokens via theme, component tokens via CSS vars — see `docs/conventions/token-conventions.md`
+- Component structure and props: see `docs/conventions/component-conventions.md`
+
+## Key references
+
+- Design spec: `docs/design-system.md`
+- Component lifecycle: `docs/reference/component-lifecycle.md`
+- Flow architecture (wizard steps, branching, fields): `documentation/flow-definition.yaml`
+- Redesigned flow spec: `documentation/steps/flow-definition.yaml` + `documentation/steps/flow-spec.md`
+- Cross-tool workflow: `docs/reference/cross-tool-workflow.md`
+
+## File ownership
+
+One file, one owner at a time. Check `docs/memory/session-log.md` before starting.
+
+- **Component source, tokens, theme, memory files:** Claude Code owns writes
+- **Visual QA, browser verification, screenshots:** Antigravity owns
+- **Shared read:** all documentation, all source files, AGENTS.md
+- **When backend agent starts:** backend owns `src/payload/`, `src/api/`; frontend agents never touch those. `documentation/flow-definition.yaml` is the shared contract.