refactor: extract browser data-import subsystem out of BrowserPanel.swift

BrowserPanel.swift carried ~3,800 lines (35% of the file) of
self-contained browser-import machinery — scope/engine/profile types,
InstalledBrowserDetector, plan/outcome models, the Chromium cookie
decryptor, BrowserDataImporter, and BrowserDataImportCoordinator with
its wizard window controller. None of it references the BrowserPanel
class.

Pure move, no logic changes:
- Sources/Panels/BrowserDataImport.swift — the entire import subsystem
- BrowserPanel.swift shrinks 10,401 -> 6,585 lines
- dedupedCanonicalURLs (fileprivate helper used only by the import
  code) moves with it

Author: arzafran

GhosttyTabs.xcodeproj/project.pbxproj

@@ -30,6 +30,7 @@
 		A5001400 /* Panel.swift in Sources */ = {isa = PBXBuildFile; fileRef = A5001410 /* Panel.swift */; };
 		A5001401 /* TerminalPanel.swift in Sources */ = {isa = PBXBuildFile; fileRef = A5001411 /* TerminalPanel.swift */; };
 		A5001402 /* BrowserPanel.swift in Sources */ = {isa = PBXBuildFile; fileRef = A5001412 /* BrowserPanel.swift */; };
+		A5FF0013 /* BrowserDataImport.swift in Sources */ = {isa = PBXBuildFile; fileRef = A5FF0003 /* BrowserDataImport.swift */; };
 		A500RG01 /* ReactGrab.swift in Sources */ = {isa = PBXBuildFile; fileRef = A500RG00 /* ReactGrab.swift */; };
 		A5001403 /* TerminalPanelView.swift in Sources */ = {isa = PBXBuildFile; fileRef = A5001413 /* TerminalPanelView.swift */; };
 		A5001404 /* BrowserPanelView.swift in Sources */ = {isa = PBXBuildFile; fileRef = A5001414 /* BrowserPanelView.swift */; };
@@ -230,6 +231,7 @@
 		A5001410 /* Panel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Panels/Panel.swift; sourceTree = "<group>"; };
 		A5001411 /* TerminalPanel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Panels/TerminalPanel.swift; sourceTree = "<group>"; };
 		A5001412 /* BrowserPanel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Panels/BrowserPanel.swift; sourceTree = "<group>"; };
+		A5FF0003 /* BrowserDataImport.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Panels/BrowserDataImport.swift; sourceTree = "<group>"; };
 		A500RG00 /* ReactGrab.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Panels/ReactGrab.swift; sourceTree = "<group>"; };
 		A5001413 /* TerminalPanelView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Panels/TerminalPanelView.swift; sourceTree = "<group>"; };
 		A5001414 /* BrowserPanelView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Panels/BrowserPanelView.swift; sourceTree = "<group>"; };
@@ -484,6 +486,7 @@
 				A5001410 /* Panel.swift */,
 				A5001411 /* TerminalPanel.swift */,
 				A5001412 /* BrowserPanel.swift */,
+				A5FF0003 /* BrowserDataImport.swift */,
 				A500RG00 /* ReactGrab.swift */,
 				A5001413 /* TerminalPanelView.swift */,
 				A5001414 /* BrowserPanelView.swift */,
@@ -788,6 +791,7 @@
 				A5001400 /* Panel.swift in Sources */,
 				A5001401 /* TerminalPanel.swift in Sources */,
 				A5001402 /* BrowserPanel.swift in Sources */,
+				A5FF0013 /* BrowserDataImport.swift in Sources */,
 				A500RG01 /* ReactGrab.swift in Sources */,
 				A5001403 /* TerminalPanelView.swift in Sources */,
 				A5001404 /* BrowserPanelView.swift in Sources */,