feat: add worktree isolation support and hook event display

Closes #152, closes #150

- Add use_worktree bool to ClaudeStartOptions and HikariConfig (Rust + TS)
- Pass --worktree flag to claude in both WSL and non-WSL command paths
- Detect WorktreeCreate/WorktreeRemove hook events in stderr handler
- Emit worktree events with distinct line_type instead of error
- Add worktree line type to TerminalLine union, Terminal rendering, and tests
- Display worktree events in green with [worktree] prefix
- Add worktree isolation toggle to Agent Settings section of ConfigSidebar
- Thread use_worktree through all seven start_claude call sites

src/lib/components/Terminal.svelte

@@ -98,6 +98,8 @@
         return "terminal-rate-limit";
       case "compact-prompt":
         return "terminal-compact-prompt";
+      case "worktree":
+        return "terminal-worktree";
       default:
         return "terminal-default";
     }
@@ -117,6 +119,8 @@
         return "[error]";
       case "rate-limit":
         return "[rate-limit]";
+      case "worktree":
+        return "[worktree]";
       default:
         return "";
     }
@@ -386,6 +390,10 @@
     color: var(--text-secondary);
   }
 
+  .terminal-worktree {
+    color: var(--terminal-worktree, #34d399);
+  }
+
   .compact-action-btn {
     display: inline-flex;
     align-items: center;