migrate agent output to capnp store, add provenance tracking

All agent output now goes to the store as nodes instead of
markdown/JSON files. Each node carries a Provenance enum identifying
which agent created it (AgentDigest, AgentConsolidate, AgentFactMine,
AgentKnowledgeObservation, etc — 14 variants total).

Store changes:
- upsert_provenance() method for agent-created nodes
- Provenance enum expanded from 5 to 14 variants

Agent changes:
- digest: writes to store nodes (daily-YYYY-MM-DD.md etc)
- consolidate: reports/actions/logs stored as _consolidation-* nodes
- knowledge: depth DB and agent output stored as _knowledge-* nodes
- enrich: experience-mine results go directly to store
- llm: --no-session-persistence prevents transcript accumulation

Deleted: 14 Python/shell scripts replaced by Rust implementations.

src/store/ops.rs

@@ -30,18 +30,25 @@ impl Store {
     /// Upsert a node: update if exists (and content changed), create if not.
     /// Returns: "created", "updated", or "unchanged".
     pub fn upsert(&mut self, key: &str, content: &str) -> Result<&'static str, String> {
+        self.upsert_provenance(key, content, Provenance::Manual)
+    }
+
+    /// Upsert with explicit provenance (for agent-created nodes).
+    pub fn upsert_provenance(&mut self, key: &str, content: &str, provenance: Provenance) -> Result<&'static str, String> {
         if let Some(existing) = self.nodes.get(key) {
             if existing.content == content {
                 return Ok("unchanged");
             }
             let mut node = existing.clone();
             node.content = content.to_string();
+            node.provenance = provenance;
             node.version += 1;
             self.append_nodes(std::slice::from_ref(&node))?;
             self.nodes.insert(key.to_string(), node);
             Ok("updated")
         } else {
-            let node = new_node(key, content);
+            let mut node = new_node(key, content);
+            node.provenance = provenance;
             self.append_nodes(std::slice::from_ref(&node))?;
             self.uuid_to_key.insert(node.uuid, node.key.clone());
             self.nodes.insert(key.to_string(), node);