Add Qwen Code provider

[brenorb]

Summary

• Add Qwen Code provider (JSONL usage parsing, settings, registration).
• Integrate across core/app/widget; add icon + docs.
• Add tests for JSONL usage aggregation.

Verification

• macOS: Qwen Code shows up in Providers and works locally.
• Vibe-coded from Codex.

Testing

• swiftformat Sources Tests
• swiftlint --strict
• pnpm check
• ./Scripts/compile_and_run.sh

Closes #247

[brenorb]

It's my first big contribution and also first 100% vibecoded with Codex (from what I learned with you so far). I hope it looks good to you.

[ratulsarna]

Thanks for adding Qwen support - the local log parsing itself looks reasonable.

Requesting changes for one core correctness issue: we currently present Qwen as if quota/reset semantics are authoritative ("% left" + "Resets in ..."), but we do not have provider-confirmed window/reset metadata for Qwen OAuth free tier. Public docs expose quota amounts, but not reset timezone/window semantics.

That means current behavior can be materially wrong (both reset countdown and percent-left math), depending on backend window definition.

Please adjust this PR to avoid false precision:

1. Remove/hide "Resets in ..." for Qwen, or explicitly mark it as unknown.
2. Remove/hide quota percent-left for Qwen (or clearly label as estimate).
3. Add an explicit docs/UI note that Qwen values are inferred from local logs and may not match backend quota windows.

Once representation is honest about uncertainty, I'm comfortable with keeping Qwen provider support.