refactor: remove SubAgent tool, make Agent use subagentModel config

Match Claude Code's architecture: a single Agent tool with subagent_type
(Explore/Plan/Verification) that uses the subagentModel setting when
no explicit model override is provided. The separate SubAgent tool is
removed since it duplicated existing functionality.

rust/crates/runtime/src/config.rs

@@ -1131,17 +1131,24 @@ impl RuntimeConfig {
     pub fn lsp_auto_start(&self) -> bool {
         self.feature_config.lsp_auto_start
     }
+<<<<<<< HEAD
 =======
     pub fn rules_import(&self) -> &RulesImportConfig {
         &self.feature_config.rules_import
     }
 >>>>>>> 22f948b7 (feat: project rules with .claw/rules/ and multi-framework auto-import)
 =======
+=======
+
+>>>>>>> 6b0af2bc (refactor: remove SubAgent tool, make Agent use subagentModel config)
     #[must_use]
     pub fn subagent_model(&self) -> Option<&str> {
         self.feature_config.subagent_model.as_deref()
     }
+<<<<<<< HEAD
 >>>>>>> 7e7baeaa (feat: SubAgent tool for fast sub-agent delegation)
+=======
+>>>>>>> 6b0af2bc (refactor: remove SubAgent tool, make Agent use subagentModel config)
 }
 
 impl RuntimeFeatureConfig {

rust/crates/rusty-claude-cli/src/setup_wizard.rs

@@ -233,7 +233,11 @@ fn prompt_fast_model(
     main_model: Option<&str>,
 ) -> Result<Option<String>, Box<dyn std::error::Error>> {
     println!();
+<<<<<<< HEAD
     println!("  \x1b[1mFast Model (for Agent subtasks)\x1b[0m");
+=======
+    println!("  Fast Model (for Agent subtasks)");
+>>>>>>> 6b0af2bc (refactor: remove SubAgent tool, make Agent use subagentModel config)
     println!("    A smaller/cheaper model used by the Agent tool when spawning");
     println!("    Explore, Plan, or Verification sub-agents. This saves tokens");
     println!("    by using a fast model for information-gathering tasks.");

rust/crates/tools/src/lib.rs

@@ -675,7 +675,7 @@ pub fn mvp_tool_specs() -> Vec<ToolSpec> {
         },
         ToolSpec {
             name: "Agent",
-            description: "Launch a background agent task that runs asynchronously. For synchronous read-only exploration, use SubAgent instead. Agent is for long-running background work that should not block the conversation.",
+            description: "Launch a specialized agent task. Use subagent_type to select the agent role: Explore (read-only search), Plan (explore + todo), Verification (explore + bash + todo), or general-purpose (full access). The agent uses subagentModel from settings if set, otherwise the default model.",
             input_schema: json!({
                 "type": "object",
                 "properties": {
@@ -4493,11 +4493,22 @@ fn build_agent_system_prompt(subagent_type: &str, model: &str) -> Result<Vec<Str
 }
 
 fn resolve_agent_model(model: Option<&str>) -> String {
-    model
-        .map(str::trim)
-        .filter(|model| !model.is_empty())
-        .unwrap_or(DEFAULT_AGENT_MODEL)
-        .to_string()
+    if let Some(m) = model.map(str::trim).filter(|m| !m.is_empty()) {
+        return m.to_string();
+    }
+    if let Some(fast) = load_subagent_model_from_config() {
+        return fast;
+    }
+    DEFAULT_AGENT_MODEL.to_string()
+}
+
+fn load_subagent_model_from_config() -> Option<String> {
+    std::env::current_dir().ok().and_then(|cwd| {
+        ConfigLoader::default_for(&cwd)
+            .load()
+            .ok()
+            .and_then(|config| config.subagent_model().map(|m| m.to_string()))
+    })
 }
 
 fn allowed_tools_for_subagent(subagent_type: &str) -> BTreeSet<String> {