refactor: render chat code blocks via CodeEditSourceEditor

[datlechin]

Summary

PR C of the AI chat redesign (docs/refactor/ai-chat-redesign.md, row C).

• Replaces the 340-line regex highlighter in AIChatCodeBlockView with a read-only CodeEditSourceEditor mount.
• SQL, JavaScript (MongoDB), and Bash (Redis) blocks now use the same tree-sitter highlighter and TableProEditorTheme as the main SQL editor, so colors track theme and font settings automatically.
• Drops the swiftlint:disable force_try suppression and the manually built NSAttributedString pipeline.
• Header buttons (Copy / Insert) and the CodeBlockGroupBoxStyle chrome are unchanged. detectLanguage(from:) keeps its public test surface.

Net change: 61 insertions, 194 deletions.

Test plan

• Open AI chat, ask for a SQL query, confirm tree-sitter highlighting matches the main editor.
• Ask for a MongoDB db.collection.find(...) snippet, confirm JavaScript highlighting.
• Ask for a Redis command, confirm bash highlighting renders.
• Code block height grows with content and caps at 400px for long snippets.
• Copy and Insert buttons still work; Insert is hidden for non-runnable languages.
• swiftlint lint --strict clean on the changed file.
• Existing AIChatCodeBlockDetectionTests still pass.

[chatgpt-codex-connector]

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