feat: initialize AIUI monorepo with project rules and core types

Foundation for the next-generation AI content surface UI:
- 16 Cursor rules files covering philosophy, Vue conventions, design system,
  content surfaces, plugin system, AI integration, renderers, security,
  Bitcoin-only policy, dev/prod modes, accessibility, performance, animation,
  mobile UX, and git workflow
- pnpm workspaces + Turborepo monorepo (@aiui/core, @aiui/app)
- Vue 3 + Vite + TypeScript + Tailwind CSS 4
- Core type system: plugins, renderers, messages, content blocks
- Plugin registry with renderer registration
- 50 mock film fixtures with search/filter utilities
- App shell with chat page layout
- Environment config templates

Made-with: Cursor

.cursor/rules/16-git-workflow.mdc

@@ -0,0 +1,52 @@
+---
+description: Git workflow - commit conventions, branching, PR process
+globs: "**/*"
+alwaysApply: false
+---
+
+# Git Workflow
+
+## Commit Messages
+Format: `type(scope): description`
+
+Types:
+- `feat`: new feature
+- `fix`: bug fix
+- `refactor`: code restructuring (no behavior change)
+- `style`: formatting, whitespace (no code change)
+- `docs`: documentation
+- `test`: adding/updating tests
+- `chore`: build, dependencies, tooling
+- `perf`: performance improvement
+
+Scope: the package or area (`core`, `app`, `plugin-x`, `renderer-film`, etc.)
+
+Examples:
+```
+feat(core): add renderer registry with lazy loading
+fix(chat): prevent scroll jump on new message
+refactor(plugin-system): simplify adapter interface
+chore(deps): update Vue to 3.6
+```
+
+## Branching
+- `main`: production-ready, always deployable
+- `dev`: integration branch for features
+- `feat/description`: feature branches (from dev)
+- `fix/description`: bug fix branches
+- `release/x.y.z`: release preparation
+
+## Pull Requests
+- One feature per PR
+- Description: what changed, why, how to test
+- All tests pass
+- TypeScript strict mode passes
+- No linter errors
+- Reviewed before merge
+
+## Rules
+- Never force push to `main` or `dev`
+- Never commit `.env.local` or any secrets
+- Never commit `node_modules`
+- Squash merge feature branches to keep history clean
+- Tag releases with semver: `v1.0.0`