feat: consume worktree field from status line hook events

Parse structured WorktreeInfo (name, path, branch, original_repo_directory)
from WorktreeCreate/Remove hook events and emit a dedicated claude:worktree
event. Store per-conversation worktree state and display an emerald branch
badge in the status bar so users can see at a glance which worktree and
branch each session is running on.

Closes #206

src-tauri/src/types.rs

@@ -296,6 +296,24 @@ pub struct AgentStartEvent {
     pub model: Option<String>,
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct WorktreeInfo {
+    pub name: String,
+    pub path: String,
+    pub branch: String,
+    pub original_repo_directory: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct WorktreeEvent {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub conversation_id: Option<String>,
+    /// "create" or "remove"
+    pub event_type: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub worktree: Option<WorktreeInfo>,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct AgentEndEvent {
     pub tool_use_id: String,