VS Code extension: inconsistent UI behavior across entry points

Problems

1. Tab bar icon opens a new sidebar group when "Preferred Location" is set to default ("Panel") — should open as a tab in the focused group's panel, not create a new group
2. "Use Terminal" setting ignored by 2 of 3 entry points (sidebar panel, permanent terminal panel) — only the tab bar button respects it
3. "Use Terminal" mode has no CLI dependency check — if claude CLI isn't installed, the user gets a raw CommandNotFoundException with no fallback or guidance
4. "Use Terminal" isn't a terminal — it opens a generic shell and auto-types claude, not a dedicated integration
5. Asymmetric code block rendering — Claude's responses show proper code blocks, user-submitted code blocks lack wrap/formatting
6. Sidebar conversation click opens correctly (tab in active group) — proving the correct behavior exists but isn't used by other entry points
7. Fresh installs broken by default — VS Code defaults to PowerShell, Windows defaults to Restricted execution policy, npm (required for CLI install) is blocked out of the box; extension doesn't account for this

Recommendations

• All entry points should open as a tab in the active editor group — reuse the sidebar's existing logic
• Remove "Use Terminal" from the extension entirely — the CLI is a separate product for users who want terminal access; the extension's value is IDE context awareness, not a shell wrapper
• Match user and Claude code block rendering