Bump workspace, inter-crate, and npm package versions 0.8.38 -> 0.8.39.

Roll CHANGELOG [Unreleased] into [0.8.39] with all fixes:
- Revert v0.8.38 /model picker rework (back to instant curated picker)
- Restore approval grouping (lossy v0.8.37 logic for approvals, exact key for denials)
- Thinking-only turn surface fix (#1727)
- ACP server JSON-RPC id stringification (#1696)
- Chat client: reasoning_content for generic providers (#1673)
- Compaction: user text query preservation (#1704)
- Engine: system prompt override survival (#1688)
- Pager: G/End overshoot fix (#1706), mouse scroll (#1716)
- Composer: scroll with text (#1677), multiline arrows (#1721)
- macOS system theme detection (#1670)
- rlm_open blank source fields (#1712)
- Terminal resize paging fix (#1724)
- Docker first-run permission (#1684)
- README Rust 1.88+ requirement note (#1718)

Tests: 3149 passed, 0 failed (deepseek-tui crate)
clippy: clean on --all-targets --all-features