[Feature Request] Add a setting to hide the pinned "BrowserOS Feedback" toolbar button

What problem does this solve? (describe the problem you're experiencing)

• BrowserOS ships a "BrowserOS Feedback" extension (bug-reporter icon, extension ID adlpneommgkgeanpaekgoaolcpncohkf, default_title: "Browser Feedback") and force-pins it to the browser toolbar.
• Right-clicking the icon and choosing Unpin/Hide does not stick: after restarting BrowserOS the button is pinned again.
• There is no setting to hide it. The Assistant and LLM Chat buttons both have toolbar visibility toggles (browseros.show_assistant, browseros.show_llm_chat in Settings → Customization), but the feedback / bug-reporter button has no equivalent, so it permanently occupies toolbar space for users who never use it.

How are you working around this today? (your current solution or workaround)

• Unpinning it again after every app restart (it reappears), or rebuilding BrowserOS locally with a patch to kBrowserOSExtensions[] to set is_pinned = false for kBugReporterExtensionId.

What's your proposed solution? (how should BrowserOS address this?)

• Add a visibility preference + a Settings → Customization toggle for the feedback button, mirroring the existing Assistant / LLM Chat switches. For example:
  • add a browseros.show_feedback_button pref in browseros_prefs.h (default true),
  • return it from GetVisibilityPrefForAction() so ShouldShowToolbarAction() gates the action,
  • and surface a "Show Feedback Button" switch next to "Show Chat Button" in Settings → Customization.
• Alternatively (or in addition): make unpinning the feedback button persist across restarts, the same way other pinned actions now do after EnsureAlwaysPinnedActions().

Additional context (optional - add screenshots, examples, or other helpful details)

• Relevant code paths:
  • packages/browseros/chromium_patches/chrome/browser/browseros/core/browseros_constants.h — kBrowserOSExtensions[] contains {kBugReporterExtensionId, /*is_pinned=*/true, false, BrowserOSExtensionProduct::kAll}.
  • packages/browseros/chromium_patches/chrome/browser/browseros/core/browseros_prefs.cc — ShouldPinBrowserOSExtension() returns IsBrowserOSPinnedExtension(extension_id) unconditionally (no pref check, no user override).
  • packages/browseros/chromium_patches/chrome/browser/ui/views/side_panel/extensions/extension_side_panel_manager.cc — "Auto-pin BrowserOS extensions to the toolbar" pins it on install/startup.
  • packages/browseros/chromium_patches/chrome/browser/ui/toolbar/pinned_toolbar/pinned_toolbar_actions_model.cc — EnsureAlwaysPinnedActions() re-pins on init; only kActionBrowserOSAgent and kActionSidePanelShowThirdPartyLlm are covered by GetVisibilityPrefForAction(), so the bug-reporter action has no visibility pref.
• Related: #239 (toolbar visibility toggles not persisting across restart), #1869 (restore BrowserOS Assistant toolbar button).