docs: add project docs, GitHub DX, fire-tools stamp

- CLAUDE.md with commands, structure, key constraints
- .claude/rules/ coding standards + workflows
- docs/architecture.md with design decisions
- .github/ CI workflow, issue templates, PR template
- LICENSE (MIT)
- .fire-tools.json initialization stamp
- README.md rewritten with features, quick start, stack table

.github/pull_request_template.md

@@ -0,0 +1,21 @@
+## Summary
+
+<!-- What does this PR change and why? -->
+
+## Type
+
+- [ ] Bug fix
+- [ ] New feature
+- [ ] Refactor
+- [ ] Docs / chore
+
+## Test plan
+
+- [ ] `pnpm lint` passes
+- [ ] `pnpm test` passes
+- [ ] `pnpm build` succeeds
+- [ ] Tested in browser (describe what you verified)
+
+## Related issues
+
+<!-- Closes #N -->