ci(studio): gate new useEffect call sites behind a per-file ratchet

.github/workflows/ci.yml

@@ -268,6 +268,10 @@ jobs:
       - run: bun run build
       - run: bun run --filter '*' typecheck
       - run: bun run typecheck:scripts
+      # `Lint` is not a required check, so a gate that only runs there cannot block a merge. The
+      # effect ban is meant to block, so the required `Typecheck` context runs it too. It is a
+      # 200ms AST pass over one package; running it twice costs nothing worth saving.
+      - run: bun run check:no-use-effect
 
   test:
     name: Test

CLAUDE.md

@@ -87,6 +87,16 @@ npx hyperframes check      # Browser gate (headless Chrome — runtime errors, l
 
 Both must pass before previewing or considering work complete.
 
+## React Rules
+
+Studio code does not call `useEffect` or `useLayoutEffect`. Derive state during render, do work in
+event handlers, fetch with a data library, and reset a subtree with a `key` instead of choreographing
+dependency arrays. For the rare one-time sync with an external system, use `useMountEffect()` from
+`packages/studio/src/hooks/useMountEffect.ts` — the one sanctioned wrapper. `bun run check:no-use-effect`
+(part of `bun run lint`) enforces this with a per-file budget seeded from the call sites that already
+existed: a new file with an effect fails, a budgeted file that grows fails, and a budgeted file that
+shrinks fails until its number is lowered, so the list can only ever be paid down.
+
 ## Project Structure
 
 ```

package.json

@@ -26,7 +26,7 @@
     "sync-schemas:check": "tsx scripts/sync-schemas.ts --check",
     "sync:package-subpaths": "node scripts/package-subpaths.mjs --write",
     "check:package-subpaths": "node scripts/package-subpaths.mjs",
-    "lint": "bun run check:docs-snippet-motion && bun run check:tracked-artifacts && bun run check:workspace-contracts && bun run check:gcp-cloud-run-dockerfile && bun run check:package-cycles && bun run check:package-subpaths && bun run check:cli-process-ownership && oxlint . && tsx scripts/lint-skills.ts && node scripts/check-skill-mirror.mjs",
+    "lint": "bun run check:docs-snippet-motion && bun run check:tracked-artifacts && bun run check:workspace-contracts && bun run check:gcp-cloud-run-dockerfile && bun run check:package-cycles && bun run check:package-subpaths && bun run check:cli-process-ownership && bun run check:no-use-effect && oxlint . && tsx scripts/lint-skills.ts && node scripts/check-skill-mirror.mjs",
     "check:gcp-cloud-run-dockerfile": "bun run --cwd packages/gcp-cloud-run test:dockerfile-workspaces",
     "lint:skills": "tsx scripts/lint-skills.ts",
     "check:skill-mirror": "node scripts/check-skill-mirror.mjs",
@@ -35,6 +35,7 @@
     "check:docs-snippet-motion": "node scripts/check-docs-snippet-motion.mjs",
     "check:workspace-contracts": "node scripts/check-workspace-contracts.mjs",
     "check:package-cycles": "node scripts/check-package-cycles.mjs",
+    "check:no-use-effect": "node scripts/check-no-use-effect.mjs",
     "check:cli-process-ownership": "node scripts/check-cli-process-ownership.mjs",
     "format": "oxfmt .",
     "test": "bun run test:unit",
@@ -48,7 +49,7 @@
     "player:perf": "bun run --filter @hyperframes/player perf",
     "format:check": "oxfmt --check .",
     "knip": "knip",
-    "test:scripts": "node --import tsx --test scripts/animejs-v4-guidance.test.mjs scripts/check-tracked-artifacts.test.mjs scripts/check-no-main-deletions.test.mjs scripts/check-docs-snippet-motion.test.mjs scripts/registry-target-paths.test.mjs scripts/check-workspace-contracts.test.mjs scripts/check-package-cycles.test.mjs scripts/check-cli-process-ownership.test.mjs scripts/check-large-files.test.mjs scripts/package-subpaths.test.mjs scripts/validate-release-channel.test.mjs scripts/publish-workflow.test.mjs scripts/install-workspace-dependencies.test.mjs scripts/draft-changelog.test.ts scripts/set-version.test.ts scripts/release-prepare.test.ts scripts/cli-options.test.ts scripts/changelog-weekly.test.ts scripts/claude-plugin-compression.test.ts scripts/catalog-payload-assets.test.ts scripts/catalog-preview-temp.test.ts scripts/player-cdn-pin.test.ts scripts/studio-runtime-smoke.test.mjs scripts/verify-packed-manifests.test.mjs scripts/lint-skills.test.mjs packages/gcp-cloud-run/check-dockerfile-workspaces.test.mjs && vitest run scripts/catalog/",
+    "test:scripts": "node --import tsx --test scripts/animejs-v4-guidance.test.mjs scripts/check-tracked-artifacts.test.mjs scripts/check-no-main-deletions.test.mjs scripts/check-docs-snippet-motion.test.mjs scripts/registry-target-paths.test.mjs scripts/check-workspace-contracts.test.mjs scripts/check-package-cycles.test.mjs scripts/check-cli-process-ownership.test.mjs scripts/check-no-use-effect.test.mjs scripts/check-large-files.test.mjs scripts/package-subpaths.test.mjs scripts/validate-release-channel.test.mjs scripts/publish-workflow.test.mjs scripts/install-workspace-dependencies.test.mjs scripts/draft-changelog.test.ts scripts/set-version.test.ts scripts/release-prepare.test.ts scripts/cli-options.test.ts scripts/changelog-weekly.test.ts scripts/claude-plugin-compression.test.ts scripts/catalog-payload-assets.test.ts scripts/catalog-preview-temp.test.ts scripts/player-cdn-pin.test.ts scripts/studio-runtime-smoke.test.mjs scripts/verify-packed-manifests.test.mjs scripts/lint-skills.test.mjs packages/gcp-cloud-run/check-dockerfile-workspaces.test.mjs && vitest run scripts/catalog/",
     "typecheck:scripts": "tsc --noEmit -p scripts/tsconfig.json",
     "test:skills": "node --test 'skills/**/*.test.mjs'",
     "generate:previews": "tsx scripts/generate-template-previews.ts",