Split ruler defaults from live settings

[pascalpp]

Implements #232 as part of #228. Threads per-ruler settings through grouped windows and rule views so Preferences edits defaults for future rulers without mutating existing managed rulers.

[pascalpp]

[codex reviewer] Two issues I would fix in this phase:

1. Active ruler background opacity can leave the foreground window faded. In RulerSettingsController.setBackgroundOpacity (Free Ruler/PreferencesController.swift:441) the controller writes settings.backgroundOpacity, then sets rulerController?.opacity to the background value. Unlike the global Preferences flow, the ruler settings sheet does not post the preferences-window closed notification or otherwise restore foreground opacity in windowWillClose (Free Ruler/PreferencesController.swift:424). Repro: open Ruler Settings for a visible ruler, move Background Opacity to 5%, close the sheet. The active ruler stays at 5% alpha until app activation changes it. I would reset to state.settings.foregroundOpacity when the sheet closes, or only preview background opacity while the app is actually backgrounded. Please add a regression test around closing the settings controller after changing the background slider.

2. The new static Ruler Settings... menu item is only added to Base.lproj/MainMenu.xib (Free Ruler/Base.lproj/MainMenu.xib:107). I do not see matching rSt-Tg-232.title entries in de/es/fi/ja/zh-hans.lproj/MainMenu.strings, and the string catalog entry for the settings window title will not localize a XIB menu title. Non-English menus will show the English label. Please add the XIB localization entries or set this title programmatically with NSLocalizedString.

[pascalpp]

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• Polish multiple ruler integration #244
• Persist and restore multiple rulers #243
• Route ruler commands to active ruler #242
• Split ruler defaults from live settings #241 👈 (View in Graphite)
• Make grouped ruler windows primary #240
• Add multi-ruler manager and lifecycle #239
• Define first-class ruler instance state #238
• feature: Support Multiple Rulers #246 : 9 other dependent PRs (#253 , #255 , #256 and 6 others)
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