feat(steer): opt-in /steer command to steer the running turn (OpenCoven#125)

Adds a discoverable `/steer <message>` command, gated behind a new off-by-
default `steer` Cargo feature (build with `--features steer`).

Behavior:
- While a turn is in flight: queue the message; it auto-runs after the current
  turn, mirroring the existing Enter-while-busy queueing (issue OpenCoven#149).
- When idle: submit the message immediately via the auto-submit path.

Implementation reuses the proven queued_messages + pending_auto_submit
mechanisms, so no new turn-dispatch logic is introduced. The command is
registered in PROMPT_SLASH_COMMANDS (feature-gated) for palette/help
discoverability, handled in the CLI main loop, and added to the
prompt_slash_commands_covers_registry allow-list (like /handoff, /stats).

Verified: builds with and without the feature; the coverage test passes in
both configurations; /steer appears in the command palette when enabled.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: BunsDev

src-rust/crates/cli/Cargo.toml

@@ -11,6 +11,9 @@ path = "src/main.rs"
 default = ["voice"]
 voice = ["claurst-core/voice", "claurst-tui/voice"]
 
+# Opt-in `/steer` command (see crates/tui). Build with `--features steer`.
+steer = ["claurst-tui/steer"]
+
 [dependencies]
 claurst-core = { workspace = true }
 claurst-api = { workspace = true }

src-rust/crates/cli/src/main.rs

@@ -2631,6 +2631,39 @@ async fn run_interactive(
                             let cmd_name = cmd_name.to_string();
                             let cmd_args = cmd_args.to_string();
 
+                            // ── /steer <message> (opt-in feature) ─────────────────────
+                            // Explicit steering: queue the message when a turn is in
+                            // flight (it auto-runs after the current turn, mirroring
+                            // Enter-while-busy), or submit it immediately when idle.
+                            #[cfg(feature = "steer")]
+                            if cmd_name == "steer" {
+                                let msg = cmd_args.trim().to_string();
+                                if msg.is_empty() {
+                                    app.notifications.push(
+                                        claurst_tui::NotificationKind::Info,
+                                        "Usage: /steer <message> — steer the running turn"
+                                            .to_string(),
+                                        Some(4),
+                                    );
+                                    continue;
+                                }
+                                if app.is_streaming || current_query.is_some() {
+                                    let preview: String = msg.chars().take(40).collect();
+                                    app.queued_messages.push_back(msg);
+                                    let total = app.queued_messages.len();
+                                    app.notifications.push(
+                                        claurst_tui::NotificationKind::Info,
+                                        format!("Steer queued ({total}): {preview}"),
+                                        Some(3),
+                                    );
+                                } else {
+                                    // Idle: submit now via the auto-submit path.
+                                    app.set_prompt_text(msg);
+                                    app.pending_auto_submit = true;
+                                }
+                                continue;
+                            }
+
                             // ── Step 1: TUI-layer intercept (overlays, toggles) ────────
                             // Run first so we know whether a UI overlay opened, which
                             // lets us suppress redundant CLI text output below.

src-rust/crates/commands/src/lib.rs

@@ -11314,7 +11314,10 @@ mod tests {
         //  - stats: intercepted directly by the TUI to open the live stats
         //    dialog; the named CLI `stats` command handles aggregate saved
         //    session reports outside the TUI.
-        const ALLOWED_ALIAS_NAMES: &[&str] = &["quit", "settings", "survey", "handoff"];
+        //  - steer: opt-in feature, intercepted directly in the CLI main loop
+        //    (queues/sends a steering message); only present when built with
+        //    `--features steer`.
+        const ALLOWED_ALIAS_NAMES: &[&str] = &["quit", "settings", "survey", "handoff", "steer"];
 
         let prompt_names: HashSet<&str> = claurst_tui::app::PROMPT_SLASH_COMMANDS
             .iter()

src-rust/crates/tui/Cargo.toml

@@ -7,6 +7,10 @@ edition.workspace = true
 # Enable real microphone capture for voice PTT mode.
 voice = ["claurst-core/voice", "dep:cpal", "dep:hound"]
 
+# Opt-in `/steer` command: explicitly queue a steering message for the running
+# turn (auto-runs after it), or submit immediately when idle. Off by default.
+steer = []
+
 # UI & Interaction features (pass-through from cc-core)
 token_budget = ["claurst-core/token_budget"]
 ultraplan = ["claurst-core/ultraplan"]

src-rust/crates/tui/src/app.rs

@@ -133,6 +133,11 @@ pub const PROMPT_SLASH_COMMANDS: &[(&str, &str)] = &[
         "status",
         "Show session status or run diagnostics (/status doctor)",
     ),
+    #[cfg(feature = "steer")]
+    (
+        "steer",
+        "Queue a steering message for the running turn (or send it now if idle)",
+    ),
     ("survey", "Open session feedback survey"),
     ("tasks", "Manage tracked background tasks"),
     (