feat: add in-place session restart via Quick Actions

[chaehyun2]

Summary

• Add "Restart Session" button to Quick Actions in session info page
• Allows users to fork the current Claude session with full conversation history (equivalent to --resume)
• Useful when a session has corrupted context (e.g. empty text blocks from image-only messages) or when the context window needs a fresh start
• Includes loading spinner on the button during restart
• Adds resumeSession RPC handler in CLI that aborts the current session and restarts with --resume
• Also fixes markdown table row misalignment (column-first → row-first layout) and prevents empty text content blocks in buildContent

Changes

• CLI: New registerResumeSessionHandler.ts, session resume state management in session.ts, resumeFromSessionId option in claudeRemote.ts
• App: sessionResume RPC call in ops.ts, Quick Actions UI in info.tsx, useSessionQuickActions hook extension
• Markdown: Table rendering fix in MarkdownView.tsx

Test plan

• Open a connected session's info page → verify "Restart Session" appears in Quick Actions
• Click "Restart Session" → verify loading spinner shows, session restarts with history preserved
• Verify the button only appears for connected (online) sessions
• Verify markdown tables with varying content lengths render with aligned rows
• Send image-only message → verify no API error about empty text blocks

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