Lint the repository with Oxlint #255

Parent Quest: #254

Story

As an effectionx contributor, I want pnpm lint to use Oxlint, so repository linting and future Effection policy rules share one static-analysis engine without changing my local or CI workflow.

Current gap

Biome currently performs repository linting. It cannot host the JavaScript policy rules intended for @effectionx/lint, so keeping it as the primary linter would require contributors and CI to operate two overlapping lint systems.

Contract

Oxlint becomes the repository’s sole linter while preserving the pnpm lint entrypoint.

• Oxlint is pinned to an exact version.
• The committed configuration explicitly declares enabled rules, severities, plugins, ignores, and overrides instead of relying on changing recommended defaults.
• Every behavior currently enforced by the Biome configuration is either represented by an equivalent Oxlint rule or recorded as an intentional migration difference.
• Existing accepted source remains clean unless a documented difference identifies a genuine issue that must be corrected.
• CI and editor integration use the committed configuration.
• Once Format the repository with Oxfmt #253 and this story are delivered, Biome has no remaining formatting or linting responsibility and is removed.

Acceptance

• pnpm lint invokes Oxlint and remains the command used by CI.
• A deliberate violation of an enabled rule makes pnpm lint fail, and correcting it makes the command pass.
• Running pnpm lint twice against an unchanged checkout produces the same diagnostics and exit status.
• The migration records the disposition of the existing Biome lint rules and overrides.
• Repository lint, typecheck, build, format, and tests pass after the migration.
• No Effection-specific policy rules are introduced by this story.

Evidence

The implementation records the rule mapping and the output of:

pnpm lint
pnpm fmt:check
pnpm check
pnpm build
pnpm test
pnpm test:node

Dependencies

• Depends on Format the repository with Oxfmt #253 so formatter churn is settled before the lint engine changes.
• Blocks the @effectionx/lint child story in Quest: Run deterministic policy validation from the effectionx README #254.

Out of scope

• Effection-specific lint rules
• Deno lint compatibility
• Executable policy documents
• README or CI policy orchestration beyond retaining the existing lint job