feat: add first-class qwen code support

[dorogao5]

Summary

Adds Qwen Code as a first-class supported agent across the main CodeDash flows without changing the zero-dependency runtime model.

What changed

• add Qwen session discovery from ~/.qwen/projects/*/(chats|sessions)/*.jsonl with version-tolerant parsing and graceful handling of missing or malformed files
• load Qwen detail into the unified transcript format used by session detail, preview, replay, search, and export paths
• include Qwen sessions in global search, replay, token analytics, running detection, launch/resume flows, handoff targets, and cross-agent conversion
• expose Qwen throughout the CLI and UI: filters, labels, running cards, install command, stats, help text, supported agents docs, and changelog
• keep cost reporting explicit: when Qwen usage metadata exists but the model has no pricing map, show token data and mark cost as unavailable instead of inventing a price

Validation

Manual checks run locally against real ~/.qwen data and a live local qwen CLI session:

• node -c src/data.js
• node -c src/convert.js
• node -c src/terminals.js
• node -c src/handoff.js
• node -c src/frontend/app.js
• node -c bin/cli.js
• git diff --check
• node bin/cli.js list 15
• node bin/cli.js show 03a66a07-3e81-4ebf-8b21-df1bf08f10ac
• node bin/cli.js search контрибьютером
• node bin/cli.js stats
• node bin/cli.js handoff 03a66a07-3e81-4ebf-8b21-df1bf08f10ac qwen
• node bin/cli.js convert 03a66a07-3e81-4ebf-8b21-df1bf08f10ac codex
• node bin/cli.js convert 17f89c71-9c2a-42cf-a68b-7c757d9b05ab qwen
• node bin/cli.js run --port=3900 --host=127.0.0.1 --no-browser
• curl http://127.0.0.1:3900/api/sessions
• curl http://127.0.0.1:3900/api/session/56fb9dab-88e6-444e-9367-a19abbea4f89
• curl http://127.0.0.1:3900/api/preview/56fb9dab-88e6-444e-9367-a19abbea4f89
• curl http://127.0.0.1:3900/api/replay/03a66a07-3e81-4ebf-8b21-df1bf08f10ac
• curl http://127.0.0.1:3900/api/search?q=контрибьютером
• curl http://127.0.0.1:3900/api/cost/56fb9dab-88e6-444e-9367-a19abbea4f89
• curl http://127.0.0.1:3900/api/active
• qwen -r 03a66a07-3e81-4ebf-8b21-df1bf08f10ac

Additional parser checks were run in an isolated temporary HOME with:

• no ~/.qwen present
• multiple Qwen JSONL shapes (chats/, sessions/, mixed timestamps)
• malformed JSONL lines
• assistant messages containing MCP tool calls and usage metadata

Known limitations

• Qwen cost stays unavailable when the stored model name has no entry in MODEL_PRICING.
• Live session mapping is strongest for explicit qwen -r <session-id> or --session-id; plain qwen still falls back to cwd and open-file detection.
• This PR does not add a dedicated automated test suite because the repository currently relies on manual validation and has no existing test harness for these flows.

[vakovalskii]

Conflicts with current codebase — app.js was split into modules. Please rebase on latest main. Also 14 files / 1000+ lines is too big for one PR — consider splitting into: 1) data.js agent support 2) frontend UI 3) terminals support.