fix(settings): Settings UI and bridge hardening

[Maxaubert]

Closes the issue for batch 7 (Low items of the 2026-10-09 review).

Fixed

• 80: unsaved-changes check compares numerically ("1.0" == "1"), as the host's SameIniValue does.
• 81: slider drags send the first value at once, then at most one write per 50 ms (trailing); release/blur flushes.
• 82: removed the unread engine/panning fields from the tray shared block (layout version 2), TrayEngine, EngineLabel.
• 83: removed the unused MPO state/set and reboot bridge messages, SetMpoDisabled, mpoNeedsRestart plumbing, HighRes restart tag; doc 09 updated.
• 88: setConfig/setConfigPersist reject keys that are not plain identifiers and values containing CR/LF/NUL (pure, unit-tested); WebView cancels navigation away from https://wind.config/ and blocks new windows.
• 91: gone with 83 (no elevated reg.exe path remains; MpoDisabledInRegistry kept, the core uses it).
• 118: Mouse speed / Pan smoothing descriptions and the ini template comments now say they do not apply in a free transform session.

Skipped

• 79: needs a new core-to-config channel for the launch model; cannot be verified safely here.

Tests

• build.bat test: 597 test cases, 597 passed | 0 failed
• build.bat, build.bat config: built
• npx playwright test in ui/: 176 passed

No version bump: bumped at merge time.

🤖 Generated with Claude Code

https://claude.ai/code/session_011zPmivSAQeivGUdBjTsaMu