[nbudin]

Summary

Replaces ESLint with oxlint for JS/TS, and with graphql-inspector for .graphql files. This supersedes the failed ESLint 10 Renovate PR (#11492).

• JS/TS: new .oxlintrc.json, generated by @oxlint/migrate from the old ESLint config and then trimmed. eslint-plugin-i18next runs as an oxlint jsPlugin (801 warnings, vs 797 under ESLint). eslint.config.mjs, eslint, and 20+ ESLint plugins/configs are removed.
• GraphQL: oxlint can't parse .graphql, so @graphql-eslint is replaced by graphql-inspector validate (yarn lint:graphql: deprecated-field warnings, --maxDepth 10).
• #import comments removed from 63 .graphql files. Codegen ignores them, but they broke the graphql-tools loader that graphql-inspector uses (and VSCode).
• CI: the eslint job (Reviewdog) is now a lint job running oxlint --format=github and yarn lint:graphql. lint-staged runs oxlint --fix.
• Oxlint errors fixed (separate commit): the React Compiler-style rules (refs, set-state-in-effect, immutability, error-boundaries) and no-unsafe-optional-chaining/no-unused-vars. Notably, scrollToItem in the form presenter read a ref during render, so it was a no-op until something re-rendered; it now resolves the ref when called.
• Tests (separate commit) for the four refactored components (DateTimeInput, MaximumEventSignupsInput, FileInputWithPreview, OpenLayersMap), verified against the pre-refactor code and by mutating the new code.

Things to know

• The CI check is renamed from eslint to lint. If branch protection requires eslint, it needs updating before merge.
• Dropped GraphQL checks: strict-id-in-types on schema.graphql and the per-field depth exemptions have no graphql-inspector equivalent. Max depth is now 10 (Inspector counts depth differently; Reports/queries.graphql fails at 8 and 9).
• Dropped lint rules: no-undef and react/require-render-return are nursery-only in oxlint; the import/resolver settings aren't carried over; eslint-config-prettier is gone with ESLint (oxlint has no formatting rules).
• TicketPurchaseForm (auto-selecting the only available product) was also refactored but isn't covered by new tests.

Test plan

• yarn oxlint app/javascript test/javascript: 0 errors (warnings only)
• yarn lint:graphql: exits 0
• yarn ts:check
• yarn vitest run: 1592 passed, 1 skipped (pre-existing)
• CI lint job passes
• Manual check: date/time input, signup limit selector, a map page, CMS file upload, ticket purchase form

Closes #11492

🤖 Generated with Claude Code

[github-actions]

Code Coverage Report: Only Changed Files listed

Package	Base Coverage	New Coverage	Difference
app/javascript/BuiltInFormControls/DateTimeInput.tsx	🟠 54.05%	🟢 94.87%	🟢 40.82%
app/javascript/CmsAdmin/CmsFilesAdmin/FileInputWithPreview.tsx	🟢 86.36%	🟢 90.91%	🟢 4.55%
app/javascript/EventsApp/ScheduleGrid/ScheduleGridContext.tsx	🟢 97.1%	🟢 96.92%	🔴 -0.18%
app/javascript/FormPresenter/ItemDisplays/FreeTextItemDisplay.tsx	🔴 23.08%	🔴 21.43%	🔴 -1.65%
app/javascript/FormPresenter/Layouts/FormPresenter.tsx	🟢 88.89%	🟢 81.82%	🔴 -7.07%
app/javascript/Maps/OpenLayersMap.tsx	🔴 0%	🟢 100%	🟢 100%
app/javascript/SignupRoundsAdmin/MaximumEventSignupsInput.tsx	🔴 0%	🟢 91.18%	🟢 91.18%
app/javascript/setupI18Next.ts	🟢 89.66%	🟢 82.76%	🔴 -6.9%
Overall Coverage	🟢 67.35%	🟢 67.54%	🟢 0.19%

Minimum allowed coverage is 0%, this run produced 67.54%