feat(maestro): route maestro send through ACP for structured sessions

Structured sessions were rejected by `send_input` with NotTerminal.
Now `run_send` checks the session view and routes to
`send_structured_prompt` for structured sessions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/maestro-cli/src/cli.rs

@@ -41,8 +41,8 @@ pub enum Command {
     Attach(AttachArgs),
     /// Kill a session by ID.
     Kill(KillArgs),
-    /// Type text into a running session, as if it had been typed on an
-    /// attached terminal.
+    /// Send text to a running session. Terminal sessions receive raw
+    /// keystrokes; structured sessions receive an ACP prompt.
     Send(SendArgs),
     /// Install or update the agent activity hook (#106).
     Hooks(HooksArgs),