refactor: remove macOS vibrancy support and unify glass surfaces

Drops the macOS vibrancy toggle, IPC, and related settings copy
Updates dialogs, popovers, tooltips, and dropdowns to use shared glass styles
Adds sticky header fade behavior to model picker and sidebar lists

packages/electron/preload.mjs

@@ -18,10 +18,6 @@ const runtimeHeadersRaw = readArgValue('--openchamber-runtime-headers');
 const homeDirectory = readArgValue('--openchamber-home');
 const macosMajorRaw = readArgValue('--openchamber-macos-major');
 const macosMajor = Number.parseInt(macosMajorRaw, 10);
-const macVibrancySupported = process.platform === 'darwin';
-// Effective state for this window (main process resolves the saved preference
-// and passes it in). Defaults on when supported unless explicitly '0'.
-const hasMacVibrancy = macVibrancySupported && readArgValue('--openchamber-mac-vibrancy') !== '0';
 const trayEnabled = process.platform !== 'darwin' || readArgValue('--openchamber-tray-enabled') !== '0';
 
 // Preload re-executes on every cross-origin navigation (we run with
@@ -97,8 +93,6 @@ if (Number.isFinite(macosMajor) && macosMajor > 0) {
 contextBridge.exposeInMainWorld('__OPENCHAMBER_ELECTRON__', {
   runtime: 'electron',
   arch: process.arch,
-  macVibrancy: hasMacVibrancy,
-  macVibrancySupported,
   trayEnabled,
 });
 
@@ -148,18 +142,6 @@ const dispatchNativeEvent = (event, detail) => {
   }
 };
 
-// Toggles the frost on/off in response to the main process around the
-// minimize/restore cycle. The default ("ready") state is set reliably in the
-// renderer (cssGenerator) — not here — because this preload runs at
-// document-start when documentElement may not exist yet.
-const setVibrancyReady = (ready) => {
-  if (!hasMacVibrancy) return;
-  try {
-    document.documentElement.toggleAttribute('data-oc-vibrancy-ready', ready === true);
-  } catch {
-  }
-};
-
 // Main-process events are read-only notifications (update progress,
 // window focus, etc.) — safe to deliver to any page rendered in this
 // webContents. The events themselves don't grant capability.
@@ -173,10 +155,6 @@ ipcRenderer.on('openchamber:emit', (_evt, payload) => {
     return;
   }
 
-  if (event === 'openchamber:vibrancy-ready') {
-    setVibrancyReady(payload.detail?.ready === true);
-  }
-
   dispatchNativeEvent(event, payload.detail);
 });