feat: implement workflow findings sharing for inter-agent communication in workflows

src/app/subagent/context.rs

@@ -2,19 +2,25 @@
 //! including the default read-only tool set for reviewer agents.
 
 use std::path::PathBuf;
+use std::sync::{Arc, Mutex};
 use super::spawn::AgentDefinition;
 
 /// Default read-only tool names granted to `role == "reviewer"` agents.
 pub const REVIEWER_ALLOWED: &[&str] = &["read", "grep", "glob", "recall", "remember"];
 
 /// Per-invocation configuration for a subagent: prompt, allowed tools,
-/// step budget, and the session directory it should operate against.
+/// step budget, session directory, and optional workflow-findings Arc
+/// for cross-agent communication within a workflow run.
 pub struct SubagentContext {
     pub system_prompt: String,
     pub allowed_tools: Vec<String>,
     pub max_steps: usize,
     pub session_dir: PathBuf,
     pub workspaces: Vec<PathBuf>,
+    /// Ephemeral findings shared between sibling subagents in the same
+    /// workflow run. Set by the workflow engine; `note_finding` writes
+    /// into this from tool code via `ToolCtx.workflow_findings`.
+    pub workflow_findings: Option<Arc<Mutex<Vec<String>>>>,
 }
 
 /// Build a `SubagentContext` from an `AgentDefinition`.
@@ -41,5 +47,6 @@ pub fn build_subagent_context(def: AgentDefinition) -> SubagentContext {
         max_steps,
         session_dir: PathBuf::new(),
         workspaces: Vec::new(),
+        workflow_findings: None,
     }
 }