Feature Description
User autocmd events fired on key plugin state changes, so configs and other plugins can react without poking at internals.

Use Case
When a diff opens, the terminal float is still visible and covers the diff buffers. Without an event to hook into, there's no clean way to auto-hide it. I'm currently matching BufWinEnter against the claudecode_diffs cache path — it works but it's fragile and depends on an internal implementation detail.

Same problem applies to connection state and terminal visibility: there's no way to know when Claude connects/disconnects or when the terminal opens/hides without overriding commands or watching buffers.

Proposed Solution
Fire doautocmd User <event> at the appropriate points. Suggested events:

• ClaudeCodeDiffOpened — when a diff view is created (_open_native_diff)
• ClaudeCodeDiffClosed — when a diff is accepted or rejected (_resolve_diff_as_saved, _resolve_diff_as_rejected)
• ClaudeCodeConnected — when the MCP socket connects (start)
• ClaudeCodeDisconnected — when the connection drops or stop is called
• ClaudeCodeTerminalOpened — when the terminal window is shown
• ClaudeCodeTerminalHidden — when the terminal window is hidden

Alternatives Considered
Matching on BufWinEnter with the cache path. Works but breaks if the path changes and isn't a stable API.

Additional Context
This opens up a clean integration surface for things like auto-hiding the terminal on diff open, triggering status line updates, or external tooling reacting to connection state.