feat(source): add Qwen CLI adapter

[ayagmar]

Objective

Add a qwen source adapter for Qwen CLI chat JSONL files.

Source shape to support

• directory-backed source under ~/.qwen/projects/**/*.jsonl
• assistant rows carry usageMetadata
• reasoning tokens are exposed separately and should be preserved
• sessionId may be absent or unreliable in the payload

Implementation plan

1. Adapter file

   • add src/sources/qwen/qwen-source-adapter.ts
   • implement SourceAdapter with id = 'qwen'

2. Discovery

   • discover JSONL files under the Qwen projects tree deterministically
   • keep the adapter directory-backed via generic --source-dir qwen=...

3. Parsing

   • stream JSONL rows and emit usage events only for assistant rows with usageMetadata
   • map token fields carefully:
     • prompt tokens -> input
     • candidate tokens -> output
     • thoughts tokens -> reasoning
     • cached content tokens -> cache read
   • keep cache write at zero unless the format truly exposes it
   • normalize timestamps and fall back to file mtime when the row timestamp is missing/invalid
   • when payload sessionId is blank/missing, derive a stable fallback from the project path + filename so unrelated sessions do not collide
   • skip zero-token rows
   • avoid advertising fixedProviderRoots unless provider pruning has a real canonical root for this source

4. Wiring

   • register qwen in src/sources/create-default-adapters.ts
   • update supported-source count/order/help expectations
   • keep the source on generic --source-dir support

5. Tests and docs

   • add tests/sources/qwen-source-adapter.test.ts
   • update shared registry/help tests and README.md

Code paths to touch

• src/sources/qwen/qwen-source-adapter.ts
• src/sources/create-default-adapters.ts
• src/utils/discover-jsonl-files.ts
• src/utils/read-jsonl-objects.ts
• src/sources/parsing-utils.ts
• src/domain/usage-event.ts
• tests/sources/qwen-source-adapter.test.ts
• tests/sources/create-default-adapters.test.ts
• tests/cli/create-cli.test.ts
• README.md

Verification

• parser fixtures cover:
  • reasoning-token capture
  • malformed-line tolerance
  • blank/missing payload session id fallback
  • timestamp fallback to file mtime
  • zero-token rows skipped
• llm-usage daily --source qwen --source-dir qwen=<fixture-dir> works
• full validation passes:
  • pnpm run lint
  • pnpm run typecheck
  • pnpm run test
  • pnpm run format:check