Subconscious: persistent agent state, store activity queries

- Agent state (outputs) persists across runs in subconscious-state.json,
  loaded on startup, saved after each run completes
- Merge semantics: each run's outputs accumulate into persistent_state
  rather than replacing
- Walked keys restored from surface agent state on load
- Store::recent_by_provenance() queries nodes by agent provenance for
  the store activity view
- Switch outputs from HashMap to BTreeMap for stable display ordering

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/mind/dmn.rs

@@ -298,6 +298,12 @@ pub struct SubconsciousSnapshot {
     pub forked_agent: Option<Arc<tokio::sync::Mutex<crate::agent::Agent>>>,
     /// Entry index where the fork diverged.
     pub fork_point: usize,
+    /// Persistent agent state — accumulated across runs.
+    pub state: std::collections::BTreeMap<String, String>,
+    /// Persistent walked keys (shared state, relevant for surface).
+    pub walked: Vec<String>,
+    /// Recent store activity for this agent: (key, timestamp), newest first.
+    pub history: Vec<(String, i64)>,
 }
 
 struct SubconsciousAgent {
@@ -311,6 +317,8 @@ struct SubconsciousAgent {
     /// Entry index where the fork diverged from the conscious agent.
     fork_point: usize,
     handle: Option<tokio::task::JoinHandle<(AutoAgent, Result<String, String>)>>,
+    /// Persistent state — accumulated across runs, serialized to disk.
+    persistent_state: std::collections::BTreeMap<String, String>,
 }
 
 impl SubconsciousAgent {
@@ -340,6 +348,7 @@ impl SubconsciousAgent {
             name: name.to_string(),
             auto, last_trigger_bytes: 0, last_run: None,
             forked_agent: None, fork_point: 0, handle: None,
+            persistent_state: std::collections::BTreeMap::new(),
         })
     }
 
@@ -353,7 +362,14 @@ impl SubconsciousAgent {
         conversation_bytes.saturating_sub(self.last_trigger_bytes) >= interval
     }
 
-    fn snapshot(&self) -> SubconsciousSnapshot {
+    fn snapshot(&self, walked: &[String], history: Vec<(String, i64)>) -> SubconsciousSnapshot {
+        // Merge persistent state with any live outputs from a running agent
+        let mut state = self.persistent_state.clone();
+        if self.is_running() {
+            for (k, v) in &self.auto.outputs {
+                state.insert(k.clone(), v.clone());
+            }
+        }
         SubconsciousSnapshot {
             name: self.name.clone(),
             running: self.is_running(),
@@ -362,6 +378,9 @@ impl SubconsciousAgent {
             last_run_secs_ago: self.last_run.map(|t| t.elapsed().as_secs_f64()),
             forked_agent: self.forked_agent.clone(),
             fork_point: self.fork_point,
+            state,
+            walked: walked.to_vec(),
+            history,
         }
     }
 }
@@ -371,6 +390,7 @@ impl SubconsciousAgent {
 pub struct Subconscious {
     agents: Vec<SubconsciousAgent>,
     pub walked: Vec<String>,
+    state_path: Option<std::path::PathBuf>,
 }
 
 impl Subconscious {
@@ -378,11 +398,57 @@ impl Subconscious {
         let agents = AGENTS.iter()
             .filter_map(|(name, _)| SubconsciousAgent::new(name))
             .collect();
-        Self { agents, walked: Vec::new() }
+        Self { agents, walked: Vec::new(), state_path: None }
     }
 
-    pub fn snapshots(&self) -> Vec<SubconsciousSnapshot> {
-        self.agents.iter().map(|s| s.snapshot()).collect()
+    /// Set the state file path and load any existing state from disk.
+    pub fn set_state_path(&mut self, path: std::path::PathBuf) {
+        if let Ok(data) = std::fs::read_to_string(&path) {
+            if let Ok(saved) = serde_json::from_str::<
+                std::collections::BTreeMap<String, std::collections::BTreeMap<String, String>>
+            >(&data) {
+                for agent in &mut self.agents {
+                    if let Some(state) = saved.get(&agent.name) {
+                        agent.persistent_state = state.clone();
+                    }
+                }
+                // Restore walked from surface agent if present
+                if let Some(surface) = self.agents.iter().find(|a| a.name == "subconscious-surface") {
+                    if let Some(walked_str) = surface.persistent_state.get("walked") {
+                        self.walked = walked_str.lines()
+                            .map(|l| l.trim().to_string())
+                            .filter(|l| !l.is_empty())
+                            .collect();
+                    }
+                }
+                dbglog!("[subconscious] loaded state from {}", path.display());
+            }
+        }
+        self.state_path = Some(path);
+    }
+
+    fn save_state(&self) {
+        let Some(path) = &self.state_path else { return };
+        let mut map: std::collections::BTreeMap<String, std::collections::BTreeMap<String, String>> =
+            std::collections::BTreeMap::new();
+        for agent in &self.agents {
+            if !agent.persistent_state.is_empty() {
+                map.insert(agent.name.clone(), agent.persistent_state.clone());
+            }
+        }
+        if let Ok(json) = serde_json::to_string_pretty(&map) {
+            let _ = std::fs::write(path, json);
+        }
+    }
+
+    pub fn snapshots(&self, store: Option<&crate::store::Store>) -> Vec<SubconsciousSnapshot> {
+        self.agents.iter().map(|s| {
+            let history = store.map(|st| {
+                let prov = format!("agent:{}", s.name);
+                st.recent_by_provenance(&prov, 30)
+            }).unwrap_or_default();
+            s.snapshot(&self.walked, history)
+        }).collect()
     }
 
     /// Collect results from finished agents, inject outputs into the
@@ -397,6 +463,7 @@ impl Subconscious {
                     None
                 }
             }).collect();
+        let had_finished = !finished.is_empty();
 
         for (idx, handle) in finished {
             let (auto_back, result) = handle.await.unwrap_or_else(
@@ -408,6 +475,10 @@ impl Subconscious {
                 Ok(_) => {
                     let name = self.agents[idx].name.clone();
                     let outputs = std::mem::take(&mut self.agents[idx].auto.outputs);
+                    // Merge into persistent state
+                    for (k, v) in &outputs {
+                        self.agents[idx].persistent_state.insert(k.clone(), v.clone());
+                    }
 
                     if let Some(walked_str) = outputs.get("walked") {
                         self.walked = walked_str.lines()
@@ -470,6 +541,9 @@ impl Subconscious {
                 Err(e) => dbglog!("[subconscious] agent failed: {}", e),
             }
         }
+        if had_finished {
+            self.save_state();
+        }
     }
 
     /// Trigger subconscious agents that are due to run.