feat(maestro): add maestro send for typing into a session

Adds POST /api/sessions/:id/input and a CLI command on top of it, so a
script (or another agent) can hand an instruction to a running session
without attaching to it.

The text goes in as one write and the Enter follows 150ms later: agents
that run a full-screen prompt coalesce a burst of input into a paste, and
a newline inside that burst becomes a line break instead of sending the
message. `--no-enter` skips the Enter and leaves the text in the prompt.

The session argument takes an ID, a unique ID prefix, or a session name;
names win over prefixes. A session whose pane has exited is refused (409)
rather than silently accepted — unlike a stray keystroke on an attach
socket, a send that goes nowhere is worth hearing about.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

crates/maestro-daemon/src/session.rs

@@ -40,6 +40,15 @@ pub const DEFAULT_LIVENESS_INTERVAL: Duration = Duration::from_secs(2);
 /// attempt, which is all #83 needs.
 pub const DEFAULT_BLOCKED_WORK_INTERVAL: Duration = Duration::from_secs(15);
 
+/// Gap between the text of a `send` and the Enter that submits it.
+///
+/// Agents that run a full-screen prompt (Claude Code, opencode) coalesce a
+/// burst of input into one paste; a newline inside that burst becomes a line
+/// break in the message instead of sending it. Landing the Enter as its own
+/// write, after the reader has drained the text, is what makes the message
+/// actually go.
+const SUBMIT_DELAY: Duration = Duration::from_millis(150);
+
 /// Per-session daemon-local bookkeeping that complements the public `Session`.
 #[derive(Debug)]
 pub struct SessionRecord {
@@ -78,6 +87,11 @@ pub enum SessionError {
     NotFound(Uuid),
     #[error("invalid environment variable name: {0:?}")]
     InvalidEnv(String),
+    /// The session exists but its pane is gone, so there is nothing to type
+    /// into. Writing to a dead session is a client bug worth reporting, unlike
+    /// a stray keystroke on an attach socket, which is dropped.
+    #[error("session is no longer running: {0}")]
+    NotRunning(Uuid),
     /// The kill was refused (#79): the session's worktree holds unsaved work.
     /// Nothing happened — the session keeps running and the tree is untouched,
     /// so it stays the operator's handle on their own unfinished work.
@@ -94,6 +108,7 @@ impl SessionError {
             SessionError::Io(_) => "io_failed",
             SessionError::NotFound(_) => "not_found",
             SessionError::InvalidEnv(_) => "invalid_env",
+            SessionError::NotRunning(_) => "not_running",
             SessionError::KillGuarded(_) => "kill_guarded",
         };
         let unsaved_work = match self {
@@ -671,6 +686,33 @@ impl SessionManager {
             .map_err(SessionError::Tmux)
     }
 
+    /// Type `text` into a session's pane, with an Enter after it when
+    /// `submit` is set.
+    ///
+    /// Unlike [`Self::send_keys`], a dead session is an error: the caller
+    /// asked for text to land somewhere, and a silent success would let a
+    /// script believe an agent had been told something it never heard.
+    pub async fn send_input(&self, id: Uuid, text: &str, submit: bool) -> Result<(), SessionError> {
+        match self.status(id).await {
+            None => return Err(SessionError::NotFound(id)),
+            Some(SessionStatus::Dead) => return Err(SessionError::NotRunning(id)),
+            Some(SessionStatus::Running) => {}
+        }
+        let tmux = self.inner.tmux.clone();
+        let bytes = text.as_bytes().to_vec();
+        tmux_blocking(move || tmux.send_keys(id, &bytes))
+            .await
+            .map_err(SessionError::Tmux)?;
+        if submit {
+            tokio::time::sleep(SUBMIT_DELAY).await;
+            let tmux = self.inner.tmux.clone();
+            tmux_blocking(move || tmux.send_keys(id, b"\r"))
+                .await
+                .map_err(SessionError::Tmux)?;
+        }
+        Ok(())
+    }
+
     /// Resize a session's window. No-op for a dead session, as with
     /// [`Self::send_keys`].
     pub async fn resize(&self, id: Uuid, cols: u16, rows: u16) -> Result<(), SessionError> {