Migrate from ESLint to oxlint

[nstepien]

Replaces ESLint with oxlint for JS/TS linting. ESLint stays only for markdown, since @eslint/markdown is built on ESLint's language plugin API, which oxlint does not support.

.oxlintrc.json was generated with @oxlint/migrate --type-aware --with-nursery and carries over 545 rules at their original warn severity. @eslint-react and sonarjs load as jsPlugins; typescript, react and vitest use oxlint's native implementations, so typescript-eslint, eslint-plugin-react-hooks and @vitest/eslint-plugin are dropped.

Scripts

before	after
node --run eslint	node --run lint (oxlint) + node --run lint:md (markdown)
node --run eslint:fix	node --run lint:fix / node --run lint:md:fix

--report-unused-disable-directives is passed to oxlint to match ESLint 9's default behaviour. CI, publish.yml, AGENTS.md and .vscode/settings.json are updated to match.

Rules that could not be migrated

• The 13 React Compiler rules (react-hooks/purity, preserve-manual-memoization, set-state-in-effect, …). oxlint only ships these as a single experimental bundled react/react-compiler rule, and will split them once they stabilise. This is the most substantive loss — happy to keep a narrow ESLint config for them alongside markdown if we'd rather not go without.
• @eslint-react/no-implicit-key, no-leaked-conditional-rendering, no-unused-props. oxlint's JS plugin API cannot supply @typescript-eslint parser services, so these throw on every file rather than running.
• @typescript-eslint/naming-convention, prefer-destructuring, no-unused-private-class-members, require-atomic-updates, one-var.

Everything else is covered, including all 40 type-aware @typescript-eslint rules via oxlint-tsgolint.

Suppressions added

Three, each a behavioural difference rather than a real defect:

• sonarjs/no-redundant-optional in src/types.ts — cannot see exactOptionalPropertyTypes without type information, so it flags the intentional ?: boolean | undefined.
• vitest/no-conditional-expect in scrollToCell.test.tsx — oxlint flags a helper function that is not a test block.
• The existing directive in src/globals.d.ts moved down one line, because oxlint reports the index signature where ESLint reported the interface.

The other 15 eslint-disable comments work unchanged — oxlint accepts the @typescript-eslint/ prefix, and the unused-directive check confirms all of them are still live.

Incidental

@eslint-react/component-hook-factories was removed: it does not exist in that plugin and ESLint silently ignored it because it was off. It was most likely meant to be react-hooks/component-hook-factories.

.agents is ignored by both linters, mirroring the existing .claude entry.

Known issue: --type-aware on Windows

oxlint 1.76.0 only looks for node_modules/.bin/tsgolint.exe, but npm writes .cmd/.ps1 shims there, so node --run lint fails locally on Windows with "Failed to find tsgolint executable". TSGOLINT_PATH does not help and 1.76.0 is the latest release. CI on ubuntu-latest is unaffected, and oxlint exits 1 rather than silently skipping the rules. Local workaround:

Copy-Item node_modules\@oxlint-tsgolint\win32-x64\tsgolint.exe node_modules\.bin\tsgolint.exe -Force

The oxc VS Code extension has an oxc.path.tsgolint setting that avoids this for editor diagnostics.

Verification

node --run lint, node --run lint:md, node --run typecheck, node --run format:check all pass, and the full suite is green (353 passed, 2 skipped across 65 files).

🤖 Generated with Claude Code

[amanmahajan7]

Worth enabling typeCheck? Would that cover all the files checked by the typecheck command?

[amanmahajan7]

Wonder if we should look into unicorn rules. Seems like it can replaces some of the the sonarjs rules

[nstepien]

I wouldn't mind removing the sonarjs rules