Qwen3 tuning, native settings redesign, log/clipboard hygiene, docs tidy

[giraphant]

Summary

• Local Qwen3 tuning.
  • The full-pass deadline is now max(5 s, 10% of audio).
  • After a warmup load, one tiny batch pass prewarms the kernels. The first full pass on a 39 s clip dropped from 1544 ms to 678 ms.
  • When Qwen3 is active, the model preloads at launch and again when routing changes.
  • The language mode still follows the user's setting; ARCHITECTURE.md now records why.
• Settings window, native design system.
  • Every pane is a grouped Form with standard controls. Custom cards, capsule tags and segmented pickers are gone.
  • 听写模型 now uses a Wi‑Fi‑style engine list with 选项… sheets. The Qwen3 sheet is modelled on 管理声音….
  • All 14 section footers became row subtitles or ⓘ popovers, and thin sections were merged.
  • The text editors now sit on the form background instead of white.
• Hygiene.
  • swift test no longer writes to the user's log file.
  • Persistent logs keep only lengths and flags; no dictation text, previews or glossary terms.
  • A deferred refinement no longer overwrites a clipboard the user changed in the meantime.
  • The order-dependent duplicate-stop test is fixed.
• Docs. README is current; AGENTS.md and ARCHITECTURE.md are consolidated; stale .gitignore entries removed and *.profraw added.

Verification

• Ran swift test: 438 tests, 0 failures. The log file got no test lines during the run.
• Ran make install and checked by hand: launch preload plus prewarm appear in the log, and the settings window was reviewed in the installed build.

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