memory: add temperature support to agent defs, update reflect prompt

Thread temperature parameter from agent def header through the API
call chain. Agents can now specify {"temperature": 1.2} in their
JSON header to override the default 0.6.

Also includes Kent's reflect agent prompt iterations.

poc-memory/src/agents/defs.rs

@@ -36,6 +36,7 @@ pub struct AgentDef {
     pub count: Option<usize>,
     pub chunk_size: Option<usize>,
     pub chunk_overlap: Option<usize>,
+    pub temperature: Option<f32>,
 }
 
 /// The JSON header portion (first line of the file).
@@ -59,6 +60,9 @@ struct AgentHeader {
     /// Overlap between chunks in bytes (default 10000)
     #[serde(default)]
     chunk_overlap: Option<usize>,
+    /// LLM temperature override
+    #[serde(default)]
+    temperature: Option<f32>,
 }
 
 fn default_model() -> String { "sonnet".into() }
@@ -79,6 +83,7 @@ fn parse_agent_file(content: &str) -> Option<AgentDef> {
         count: header.count,
         chunk_size: header.chunk_size,
         chunk_overlap: header.chunk_overlap,
+        temperature: header.temperature,
     })
 }