chat: honor the per-session cwd for Super Admin (was hardcoded to home)

claude-manager pinned the spawn cwd to HOST_HOME for Super Admin, ignoring the
cwd passed from the chat handler — so /chat sessions ran in /home/pastilhas
regardless. Now it uses params.cwd when provided (falling back to HOST_HOME),
so /chat actually runs from the dedicated claude_sessions directory.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/servers/sidecar/protocol.ts

@@ -61,6 +61,7 @@ export type ClaudeSpawnParams = {
   sessionKey: string;
   model?: string;
   role?: string;
+  cwd?: string;
 };
 
 export type ClaudeSpawnStreamingParams = {