Summary

• Handle Ghostty open_url actions for local filesystem paths directly in the app, so plain terminal paths can be opened immediately instead of only being stored in transient Ghostty state.
• Introduce ghosttyOpenURLRequest to normalize Ghostty URL payloads into either passthrough remote URLs or standardized local file URLs, covering plain absolute paths, relative paths, paths with spaces, and tilde-prefixed paths similar to Supaterm.
• Preserve Foundation tilde expansion semantics for local file paths, including named home directories like ~user/..., by relying on NSString(...).expandingTildeInPath instead of concatenating onto the current user home path.
• Keep worktree path normalization aligned with that same Foundation behavior by asserting named-tilde expansion in the existing path helpers, so repository and global worktree settings continue to resolve ~user/... correctly.

Test plan

• In a terminal surface, activate an https://... link and verify it still opens in the browser instead of being treated as a local file path.
• In a terminal surface, activate a plain absolute local path and verify the corresponding file or folder opens correctly.
• In a terminal surface, activate a ~/... local path and verify it resolves against the current user home directory.
• In a terminal surface, activate a ~user/... local path and verify it resolves to that named user home directory rather than being appended to the current user home path.
• In Worktree settings, enter a base directory using ~user/..., save, reopen the setting, and verify the resolved path and example worktree path still point at the named user home.

Closes #234