fix(tui): make prompt suggestion configurable (opt-in, default off)

- Add prompt_suggestion: Option<bool> config field with
  prompt_suggestion_enabled() accessor (defaults to false)
- Guard suggestion generation behind the config check
- Use config.default_model() (provider-aware) instead of hardcoded
  deepseek-v4-flash to avoid cross-provider data egress
- Document in config.example.toml

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

config.example.toml

@@ -144,6 +144,7 @@ memory_path = "~/.codewhale/memory.md"
 allow_shell = true
 approval_policy = "on-request" # on-request | untrusted | never
 sandbox_mode = "workspace-write" # read-only | workspace-write | danger-full-access | external-sandbox
+# prompt_suggestion = true  # opt-in: show ghost-text follow-up question in composer after each turn
 
 # Typed permission rules live in a sibling `permissions.toml` file, not in
 # config.toml. This schema slice is ask-only and is parsed for follow-up

crates/tui/src/config.rs

@@ -1550,6 +1550,9 @@ pub struct Config {
     /// missing optional file doesn't fail the launch.
     pub instructions: Option<Vec<String>>,
     pub allow_shell: Option<bool>,
+    /// Opt-in ghost-text follow-up prompt suggestion after each completed turn.
+    /// Default: false — the user must explicitly set this to true to enable.
+    pub prompt_suggestion: Option<bool>,
     pub approval_policy: Option<String>,
     pub sandbox_mode: Option<String>,
     pub yolo: Option<bool>,
@@ -2707,6 +2710,11 @@ impl Config {
         self.allow_shell.unwrap_or(false)
     }
 
+    /// Whether ghost-text prompt suggestion is enabled (opt-in, default off).
+    pub fn prompt_suggestion_enabled(&self) -> bool {
+        self.prompt_suggestion.unwrap_or(false)
+    }
+
     /// Return the maximum number of concurrent sub-agents.
     /// Checks `[subagents] max_concurrent` first, then top-level `max_subagents`,
     /// then falls back to `DEFAULT_MAX_SUBAGENTS`.
@@ -4253,6 +4261,7 @@ fn merge_config(base: Config, override_cfg: Config) -> Config {
         // both — they list `~/global.md` inside the project array.
         instructions: override_cfg.instructions.or(base.instructions),
         allow_shell: override_cfg.allow_shell.or(base.allow_shell),
+        prompt_suggestion: override_cfg.prompt_suggestion.or(base.prompt_suggestion),
         yolo: override_cfg.yolo.or(base.yolo),
         approval_policy: override_cfg.approval_policy.or(base.approval_policy),
         sandbox_mode: override_cfg.sandbox_mode.or(base.sandbox_mode),

crates/tui/src/tui/ui.rs

@@ -1843,11 +1843,13 @@ async fn run_event_loop(
 
                         // Generate ghost-text follow-up suggestion asynchronously.
                         if status == crate::core::events::TurnOutcomeStatus::Completed
+                            && config.prompt_suggestion_enabled()
                             && app.api_messages.len() >= 2
                         {
                             let suggestion_cell = app.prompt_suggestion_cell.clone();
                             let api_key = config.deepseek_api_key().unwrap_or_default();
                             let base_url = config.deepseek_base_url();
+                            let model = config.default_model();
                             let messages: Vec<crate::models::Message> = app.api_messages.clone();
                             let gen_token = app
                                 .prompt_suggestion_gen
@@ -1860,10 +1862,7 @@ async fn run_event_loop(
                                         );
                                     if let Some(suggestion) =
                                         crate::tui::prompt_suggestion::generate_suggestion(
-                                            &api_key,
-                                            &base_url,
-                                            "deepseek-v4-flash",
-                                            &summary,
+                                            &api_key, &base_url, &model, &summary,
                                         )
                                         .await
                                         && let Ok(mut guard) = suggestion_cell.lock()