ci: wire Biome as the linter (replace never-installed eslint)

[kazukinakai]

Why

The org reusable CI (node-pnpm-ci.yml, adopted in #4) runs pnpm turbo run build lint test, but lint was guaranteed to fail: every workspace package shipped a "lint": "eslint ..." script while eslint was never installed anywhere in this fork (no devDependency, absent from pnpm-lock.yaml), and the leftover root .eslintrc.json never actually ran. The org standard linter is Biome (see the agiletec repo).

#4 merged the CI workflow to main but did not fix the eslint wiring, so ci / ci is currently red on main. This PR makes pnpm turbo run lint pass.

What

• Add @biomejs/biome@^2.4.16 to root devDependencies (no pnpm catalog in this repo, so pinned literally).
• Add biome.json replicating agiletec's curated ruleset (recommended: false + error-level rules), formatter, and vcs blocks; files.includes adapted to this layout.
• Replace "eslint ..." with "biome check ." in all 20 package lint scripts (packages/gemini-core keeps its echo no-op by design).
• Remove the orphaned .eslintrc.json.
• Apply biome check --write (formatting + safe fixes) and fix the residual real violations: unused catch bindings, escape/shadowed-global renames, redundant test non-null assertions, a placeholder async generator, and a generic-T cast where biome's Object.hasOwn safe-fix outran tsc.

Rules tuned for inherited Qwen-fork code

• noControlCharactersInRegex: off — terminal/ANSI handling intentionally matches control chars (every hit carried an eslint-disable no-control-regex).
• noUndeclaredVariables: off — redundant with tsc and misfires on TS type references; mirrors agiletec's TypeScript override.
• noExplicitAny / noEmptyBlockStatements: warn — too noisy to gate on now across the fork; kept visible as warnings for later cleanup.

Verification

• pnpm turbo run lint → 2 successful, 2 total (the two workspace packages, @airiscode/cli + @airiscode/core).

Pre-existing failures (NOT addressed here — out of lint scope)

ci / ci runs build lint test. Two pre-existing, unrelated failures remain (they were masked in #4's run because turbo fail-fast aborted on the eslint error first):

1. @airiscode/cli#build fails error TS17004: Cannot use JSX unless the '--jsx' flag is provided — the airis-generated tsconfig.base.json has no jsx option but the CLI uses Ink/React JSX. Fix belongs in manifest.toml [typescript] + airis gen (or a hand-set jsx in the generated tsconfig).
2. @airiscode/core#test (and cli) fail MISSING DEPENDENCY '@vitest/coverage-v8' — the vitest config requests coverage but the provider is not installed anywhere. Fix: add @vitest/coverage-v8 devDep (or drop coverage from the vitest config).

These block full ci / ci green and should be handled separately.