build: add eslint config and lint script

[TheGreatAxios]

Summary

• Stacked on test: use inference-testing fakes and add e2e retry, base64, live suites #11.
• eslint.config.ts matches corbits-ollama-adapter; eslint, @eslint/js, typescript-eslint and jiti at the same versions; lint script.
• CI runs bun run lint and prettier --check .; markdown is formatted and IMPLEMENTATION.md lists the eslint dev dependencies.

Verification

• bun run lint, prettier, typecheck, build and bun run test (16 pass); CI passes.

Closes CL-9069

[TheGreatAxios]

Review

Independent review of the stack found: bad base64 replies escaped as a raw DOMException or silently truncated vectors; non-integer indices were accepted; duplicate-index and non-JSON-200 coverage was lost; the live suite failed instead of skipping when the model was absent. All fixed in this stack (strict base64 decode, number.integer index, restored harness tests, model-aware skip).

Remaining notes: peer range >=0.4.0 follows sibling convention. Each commit typechecks, tests, and builds standalone.

[TheGreatAxios]

Superseded: oxfmt and oxlint replace ESLint and Prettier in this repo.

[TheGreatAxios]

Reopened only so the stack merges in order: later PRs are built on this branch. The oxfmt/oxlint PR higher in the stack removes this ESLint setup, so main ends up with oxc only.