Auto-run tests on playground load

[thejchap]

Context

Closes #137 — when the playground loads, automatically run the tests instead of leaving an empty terminal until the user clicks Run.

Changes

• Auto-run on load (playground/src/Editor/Chrome.tsx): a one-shot effect fires handleRun() as soon as the WASM discovery module is ready. The run spins up the Pyodide worker itself, so execution starts the moment Python can run. A didAutoRunRef guard ensures it fires only on the initial load, not on later re-renders/edits.
• Hermetic playground lint/format pre-commit hooks (.pre-commit-config.yaml): the eslint and prettier hooks moved from bash -c 'cd playground && bun run …' (needs bun + a pre-installed node_modules) to language: node with pinned additional_dependencies, mirroring the existing markdownlint-cli2 hook so prek installs the toolchain itself.
• CommonJS eslint config (playground/eslint.config.cjs, replacing eslint.config.js): required so the hook can resolve its plugins from prek's hermetic node env — prek exposes the env via NODE_PATH, which ESM imports ignore but require() honors. ESLint still auto-discovers the .cjs config for local eslint src/, so bun run lint is unaffected.

Test plan

• uvx prek run eslint --all-files → Passed
• uvx prek run prettier --all-files → Passed
• Verified local eslint src/ auto-discovers eslint.config.cjs (the lint/format npm scripts still work).
• Note: a full tsc/Vite build wasn't run here — the WASM toolchain (wasm-pack, wasm32 target) isn't available in this environment, and the change is a small isolated React effect that passes ESLint's rules-of-hooks/exhaustive-deps.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR improves the playground’s first-load experience by automatically running the default tests as soon as the WASM discovery module is ready, and it updates pre-commit hooks to run ESLint/Prettier hermetically (without requiring bun or a pre-installed node_modules).

Changes:

• Auto-run tests once on initial playground load after WASM init (Chrome.tsx).
• Switch pre-commit ESLint/Prettier hooks to language: node with pinned additional_dependencies.
• Replace the playground ESLint flat config from ESM (eslint.config.js) to CommonJS (eslint.config.cjs) so plugin resolution works in prek’s hermetic node environment.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
playground/src/Editor/Chrome.tsx	Adds a guarded effect that triggers an initial test run once WASM is ready.
playground/eslint.config.js	Removes the ESM flat config (replaced by CJS).
playground/eslint.config.cjs	Adds a CJS flat config compatible with prek’s NODE_PATH-based resolution.
.pre-commit-config.yaml	Updates ESLint/Prettier hooks to hermetic node environments with pinned deps.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.