Added rules for Git Copilot

.github/commands/start-dev.md

@@ -0,0 +1,18 @@
+# start-dev
+
+Custom command for local development startup in GitHub Copilot environment.
+
+## Steps
+
+```zsh
+yarn install
+yarn start
+```
+
+Docs site only:
+
+```zsh
+cd dev-docs
+yarn install
+yarn start
+```

.github/commands/test-watch.md

@@ -0,0 +1,15 @@
+# test-watch
+
+Custom command to run app tests in watch mode.
+
+## Steps
+
+```zsh
+yarn test:app
+```
+
+Single pass mode:
+
+```zsh
+yarn test:app --watch=false
+```

.github/commands/verify-ci.md

@@ -0,0 +1,19 @@
+# verify-ci
+
+Custom command to run local checks closest to CI gates.
+
+## Steps
+
+```zsh
+yarn test:typecheck
+yarn test:code
+yarn test:app --watch=false
+```
+
+If docs were changed:
+
+```zsh
+cd dev-docs
+yarn install
+yarn build
+```

.github/rules/conventions.md

@@ -0,0 +1,15 @@
+# conventions
+
+- Keep changes small and scoped to the requested behavior.
+- Follow existing folder and naming patterns before introducing new abstractions.
+- Prefer TypeScript with immutable values (`const`, `readonly`).
+- Use optional chaining (`?.`) and nullish coalescing (`??`) where it reduces branching.
+
+## How to verify
+
+```zsh
+yarn test:code
+```
+
+- Confirm no new lint violations.
+- Confirm changed files follow existing naming conventions.

.github/rules/data-restore.md

@@ -0,0 +1,14 @@
+# data-restore
+
+- Do not change persisted data shape without a migration plan.
+- Keep backward compatibility for scene/app restore paths.
+- Add regression coverage when import/export or restore logic changes.
+
+## How to verify
+
+```zsh
+yarn test:app --watch=false
+```
+
+- Open an older scene JSON and confirm it loads without runtime errors.
+- Re-export and re-import the same scene; confirm element count and bindings stay stable.

.github/rules/do-not-touch.md

@@ -0,0 +1,16 @@
+# do-not-touch
+
+Sensitive paths require explicit approval before edits:
+
+- `.github/workflows/`
+- `firebase-project/`
+- release/build automation under `scripts/`
+- secret management or environment configuration flows
+
+## How to verify
+
+- Run a diff scoped to sensitive paths and confirm no accidental edits.
+
+```zsh
+git --no-pager diff -- .github/workflows firebase-project scripts
+```

.github/rules/excalidraw-app.md

@@ -0,0 +1,13 @@
+# excalidraw-app
+
+- Keep UI/product behavior changes isolated inside `excalidraw-app/` when possible.
+- Use functional components and hooks; do not break hook rules.
+- Prefer existing state patterns already used in the app.
+
+## How to verify
+
+```zsh
+yarn test:app --watch=false
+```
+
+- Smoke-test the changed flow in local app start.

.github/rules/i18n-locales.md

@@ -0,0 +1,13 @@
+# i18n-locales
+
+- Do not hardcode user-facing strings if localization keys are expected.
+- Keep translation keys stable; avoid unnecessary renames.
+- When adding UI text, update related locale entries.
+
+## How to verify
+
+```zsh
+yarn locales-coverage
+```
+
+- Check that newly added keys exist in required locale files.

.github/rules/packages-element-math.md

@@ -0,0 +1,15 @@
+# packages-element-math
+
+- Keep `packages/element` and `packages/math` changes bounded and benchmark-aware.
+- Prefer low-allocation implementations in geometry/math hotspots.
+- Use shared types from `packages/math/src/types.ts` (`Point` for coordinates).
+- Add tests for edge cases and precision-sensitive operations.
+
+## How to verify
+
+```zsh
+yarn --cwd ./packages/math test
+yarn --cwd ./packages/element test
+```
+
+- Run targeted tests for changed geometry paths if available.

.github/rules/project-architecture.md

@@ -0,0 +1,14 @@
+# project-architecture
+
+- Preserve package boundaries under `packages/`.
+- Avoid circular dependencies between packages and app layers.
+- Keep public APIs stable unless a breaking change is explicitly requested.
+
+## How to verify
+
+```zsh
+yarn test:typecheck
+yarn test:code
+```
+
+- Confirm imports remain one-directional according to existing boundaries.

.github/rules/security.md

@@ -0,0 +1,14 @@
+# security
+
+- Never commit secrets, tokens, or credentials.
+- Treat all external input as untrusted and validate/sanitize it.
+- Prefer least-privilege settings for config changes.
+- Upgrade vulnerable dependencies with minimal blast radius.
+
+## How to verify
+
+```zsh
+git --no-pager grep -nE "(api[_-]?key|secret|token|password)" -- ':!yarn.lock'
+```
+
+- Ensure no new sensitive literals were introduced.

.github/rules/testing.md

@@ -0,0 +1,15 @@
+# testing
+
+- Every behavior change must include updated or new tests.
+- Bug fixes require at least one regression test when feasible.
+- Keep tests deterministic and independent.
+
+## How to verify
+
+```zsh
+yarn test:app --watch=false
+yarn test:typecheck
+yarn test:code
+```
+
+- Confirm changed code paths are covered by at least one automated test.

dev-docs/ab-validation-rules.md

@@ -0,0 +1,35 @@
+# A/B validation rules
+
+## Goal
+
+Validate whether the repository guidance format is usable for GitHub Copilot workflows (A) versus Cursor-oriented layout assumptions (B).
+
+## Test scenario
+
+- Scope: docs-only setup for agent rules and commands.
+- Inputs: command docs, rule docs, onboarding docs.
+- Success criteria:
+  - At least 6 rule files with `How to verify` section.
+  - At least 2 custom command docs.
+  - Onboarding docs clearly describe project context and conventions.
+
+## Variant A (GitHub Copilot structure)
+
+- Paths used: `.github/commands/`, `.github/rules/`, `onboarding-docs/`.
+- Result:
+  - 9 rule files present, each with `How to verify`.
+  - 3 command docs present.
+  - `AGENTS.md` and `CLOUDE.MD` present.
+- Status: PASS.
+
+## Variant B (Cursor-only path expectation)
+
+- Paths expected: `.cursor/commands/`, `.cursor/rules/`.
+- Result:
+  - Not applied in this repository by design.
+  - Would duplicate the source of truth and diverge from Copilot instructions.
+- Status: FAIL (intended).
+
+## Conclusion
+
+Use Variant A as the canonical setup for this repository because the active tooling is GitHub Copilot, not Cursor.

excalidraw-app/package.json

@@ -52,6 +52,7 @@
     "build:preview": "yarn build && vite preview --port 5000"
   },
   "devDependencies": {
+    "cross-env": "7.0.3",
     "vite-plugin-sitemap": "0.7.1"
   }
 }

onboarding-docs/AGENTS.md

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+# AGENTS
+
+## Project context
+
+- Repository: Excalidraw monorepo.
+- Main areas:
+  - `excalidraw-app/` - main web app.
+  - `packages/` - shared libraries (`common`, `math`, `element`, `excalidraw`, `utils`).
+  - `examples/` - integration and usage examples.
+  - `dev-docs/` - documentation site and internal docs.
+
+## Active assistant environment
+
+- Primary assistant: GitHub Copilot (JetBrains workspace).
+- Canonical AI guidance file: `.github/copilot-instructions.md`.
+- Command docs: `.github/commands/`.
+- Rule docs: `.github/rules/`.
+
+## Common commands
+
+```zsh
+yarn start
+yarn build
+yarn test:app --watch=false
+yarn test:typecheck
+yarn test:code
+```
+
+Docs workflow:
+
+```zsh
+cd dev-docs
+yarn install
+yarn start
+```
+
+## Architecture notes
+
+- Keep package boundaries explicit; avoid circular dependencies.
+- Prefer local changes near feature ownership (avoid broad cross-cutting edits).
+- Treat serialized/imported scene data compatibility as a stability contract.
+
+## Coding conventions
+
+- TypeScript-first for new code.
+- Favor immutable data (`const`, `readonly`) and small focused components.
+- Use optional chaining (`?.`) and nullish coalescing (`??`) where helpful.
+- For math-related changes, use shared types from `packages/math/src/types.ts` and prefer `Point`.
+
+## Quality gates
+
+- Minimum local verification before PR:
+
+```zsh
+yarn test:typecheck
+yarn test:code
+yarn test:app --watch=false
+```
+
+- Build gate:
+
+```zsh
+yarn build
+```

onboarding-docs/CLOUDE.MD

@@ -0,0 +1,17 @@
+# CLOUDE
+
+## Purpose
+
+Compatibility onboarding note for teams that previously used `CLAUDE.md`-style files.
+
+## Source of truth in this repository
+
+- `.github/copilot-instructions.md`
+- `.github/commands/`
+- `.github/rules/`
+- `dev-docs/ab-validation-rules.md`
+- `onboarding-docs/AGENTS.md`
+
+## Important
+
+Do not create parallel Cursor-only rule trees for this repo unless explicitly required. This repository is configured for GitHub Copilot-first workflows.