memory: add agent-context placeholder, split context groups

Add `agent: bool` field to ContextGroup (default true) so agents get
personality/identity context without session-specific groups (journal,
where-am-i). Agents now get the full identity.md, reflections.md,
toolkit, etc. instead of the compact core-personality loader.

New {{agent-context}} placeholder resolves all agent-tagged groups
using the same get_group_content() as load-context.

poc-memory/src/agents/defs.rs

@@ -412,6 +412,25 @@ fn resolve(
             Some(Resolved { text, keys: vec![] })
         }
 
+        // agent-context — personality/identity groups from load-context config
+        "agent-context" => {
+            let cfg = crate::config::get();
+            let mut text = String::new();
+            let mut keys = Vec::new();
+            for group in &cfg.context_groups {
+                if !group.agent { continue; }
+                let entries = crate::cli::misc::get_group_content(group, store, &cfg);
+                for (key, content) in entries {
+                    use std::fmt::Write;
+                    writeln!(text, "--- {} ({}) ---", key, group.label).ok();
+                    writeln!(text, "{}\n", content).ok();
+                    keys.push(key);
+                }
+            }
+            if text.is_empty() { None }
+            else { Some(Resolved { text, keys }) }
+        }
+
         // node:KEY — inline a node's content by key
         other if other.starts_with("node:") => {
             let key = &other[5..];