refactor: replace CodeEditSourceEditor with native NSTextView editor

[datlechin]

Summary

• Replace CodeEditSourceEditor/CodeEditTextView (252 files, 1.5GB, 25K+ LOC third-party) with a native NSTextView-based SQL editor (~1,500 LOC)
• Fix horizontal scrolling (bug: Home and End keys don't work in the SQL editor #448) — root cause was a variable shadowing bug in CETV where maxLineWidth was never updated
• Fix Home/End keys (bug: Home and End keys don't work in the SQL editor #448) — now handled natively by NSTextView

New editor architecture (Apple-standard patterns)

Component	File	LOC	Apple Pattern
TPTextView	Views/Editor/TPTextView.swift	227	NSTextView subclass (minimal overrides)
TPSyntaxHighlighter	Views/Editor/TPSyntaxHighlighter.swift	455	Temporary attributes on NSLayoutManager
TPLineNumberView	Views/Editor/TPLineNumberView.swift	518	NSRulerView subclass
TPEditorView	Views/Editor/TPEditorView.swift	204	NSViewRepresentable
TPEditorTheme	Views/Editor/TPEditorTheme.swift	33	Value type
TPEditorConfiguration	Views/Editor/TPEditorConfiguration.swift	43	Value type
TPEditorDelegate	Views/Editor/TPEditorDelegate.swift	20	Protocol with defaults

What we gain for free from NSTextView

• Horizontal scrolling via NSTextContainer.widthTracksTextView = false (no workarounds)
• Find/Replace via usesFindBar = true (built-in, zero code)
• Home/End keys (built-in NSResponder)
• Undo/Redo via allowsUndo = true (built-in NSUndoManager)
• Accessibility (VoiceOver)
• Large file performance via allowsNonContiguousLayout = true

Files changed

• 7 new TP* editor files (1,496 LOC)
• 20 modified — adapted Vim mode, AI suggestions, event routing, completion, theme, coordinator to NSTextView API; replaced CursorPosition with NSRange
• 252+ deleted — LocalPackages/CodeEditSourceEditor, LocalPackages/CodeEditLanguages, TableProEditorTheme.swift

Test plan

• Type SQL — syntax highlighting works (keywords, strings, comments, numbers)
• Paste long line — horizontal scrolling works
• Cmd+F — Find Bar appears
• Cmd+Z — undo works
• Home/End keys — cursor moves to line start/end
• Enable Vim mode — Normal/Insert/Visual modes work
• AI inline suggestions — ghost text appears after typing
• Right-click — AI context menu (Explain, Optimize)
• Line numbers — display and update correctly
• Word wrap toggle — switches between wrap and horizontal scroll
• Large file (>100KB) — no freeze
• Tab switch — editor state preserved
• Read-only previews (SQL Review, SQL Import) — display with highlighting

Closes #448