Add explicit Tweaks defaults workflow

[jamesrochabrun]

What changed

• keep Tweaks changes live and in memory until reload instead of writing every interaction
• add explicit Reset and Save as defaults actions with saving and inline failure states
• write changed defaults atomically and reject source/schema drift
• show a loading state on the Tweaks button without the previous SF Symbol
• make Ideas generation additive, inventory existing controls, and reject generated updates that remove or alter them
• remove the explicit popover height cap so the panel can size naturally
• pin all Canvas consumers and lockfiles to exact release 1.3.2

Why

Live experimentation and persisted project defaults were previously coupled, and running Ideas again could replace existing controls. The panel also inherited unclear button styling and could clip content under a fixed maximum height.

Impact

Tweaks now have a clear lifecycle: temporary values survive panel dismissal, reload restores source defaults, Reset restores the current baseline, and Save as defaults explicitly promotes live values to source. Additive Ideas preserve existing controls.

Dependency

Canvas 1.3.2 is published and pinned exactly at revision 7c489d3.

Validation

• Canvas swift test — 172 tests passed
• EaselWebInspector swift test — 208 tests passed against Canvas 1.3.2
• EaselPreview swift test — 3 tests passed against Canvas 1.3.2
• Easel Debug macOS xcodebuild — succeeded against Canvas 1.3.2
• standalone EaselChat test build is currently blocked before project tests by the existing CodeEditSymbols Bundle.module resource issue