feat(auth): show plugin version in login menu

[sunerpy]

Summary

• read the plugin version from the packaged package.json
• display it in the Kiro authentication method menu
• cover package-version and auth-label behavior with tests

Verification

• bun test (797 passed)
• bun run typecheck
• bun run build
• bunx prettier --check 'src/**/*.ts'\n- real opencode auth login -p kiro-auth menu displays plugin v0.14.2\n- npm pack --dry-run --json includes dist/version.js and package.json

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/version.ts	83.33%	2 Missing ⚠️

Files with missing lines	Coverage Δ
src/core/auth/auth-handler.ts	85.53% <100.00%> (+0.06%)	⬆️
src/version.ts	83.33% <83.33%> (ø)

... and 1 file with indirect coverage changes

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