feat: enhance workspace management and history tracking in application state

src/app/subagent/context.rs

@@ -14,6 +14,7 @@ pub struct SubagentContext {
     pub allowed_tools: Vec<String>,
     pub max_steps: usize,
     pub session_dir: PathBuf,
+    pub workspaces: Vec<PathBuf>,
 }
 
 /// Build a `SubagentContext` from an `AgentDefinition`.
@@ -23,8 +24,8 @@ pub struct SubagentContext {
 /// fall back to an empty list (i.e. "all tools allowed") for other roles.
 /// `max_steps` is read from the definition, defaulting to 25 if absent.
 ///
-/// Return: a context with empty `system_prompt` and `session_dir`,
-/// resolved `max_steps`, and the resolved allowed-tool list.
+/// Return: a context with empty `system_prompt`, empty `workspaces`,
+/// empty `session_dir`, resolved `max_steps`, and the resolved allowed-tool list.
 pub fn build_subagent_context(def: AgentDefinition) -> SubagentContext {
     let allowed_tools = def.allowed_tools.clone().unwrap_or_else(|| {
         if def.role == "reviewer" {
@@ -39,5 +40,6 @@ pub fn build_subagent_context(def: AgentDefinition) -> SubagentContext {
         allowed_tools,
         max_steps,
         session_dir: PathBuf::new(),
+        workspaces: Vec::new(),
     }
 }