identity: load ContextSource::Store from graph, not flat files

ContextSource::Store was handled identically to File — reading .md
files from disk. Now uses MemoryNode::load() to read from the capnp
store. This is why personality wasn't showing correctly in poc-agent:
store-sourced context groups (cognitive-modes, stuck-toolkit,
instructions, memory-instructions-core) were being looked up as
flat files and silently missing.

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

src/agent/identity.rs

@@ -93,11 +93,17 @@ fn load_memory_files(cwd: &Path, memory_project: Option<&Path>, context_groups:
                 // Journal loading handled separately
                 continue;
             }
-            ContextSource::File | ContextSource::Store => {
+            ContextSource::Store => {
-                // File source - load each key as a file
+                // Load from the memory graph store
+                for key in &group.keys {
+                    if let Some(node) = crate::hippocampus::memory::MemoryNode::load(key) {
+                        memories.push((key.clone(), node.content));
+                    }
+                }
+            }
+            ContextSource::File => {
                 for key in &group.keys {
                     let filename = format!("{}.md", key);
-                    // Try config dir first, then project, then global
                     if let Some(content) = read_nonempty(&config_dir.join(&filename)) {
                         memories.push((key.clone(), content));
                     } else if let Some(content) = load_memory_file(&filename, project.as_deref(), &global) {
@@ -105,7 +111,6 @@ fn load_memory_files(cwd: &Path, memory_project: Option<&Path>, context_groups:
                     }
                 }
             }
-            // All variants covered
         }
     }