Split journal tools from default definitions, expose to all for now

journal_definitions() separated from definitions() in memory.rs.
All agents get memory + journal tools via memory_and_journal_definitions().
TODO: implement per-agent tool whitelist from header to properly
restrict journal tools to journal agent only.

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

src/thought/memory.rs

@@ -57,6 +57,12 @@ pub fn definitions() -> Vec<ToolDef> {
                 "key":{"type":"string","description":"Output name (e.g. 'relevant_memories')"},
                 "value":{"type":"string","description":"Output value"}
             },"required":["key","value"]})),
+    ]
+}
+
+/// Journal-only tools — only given to the journal agent
+pub fn journal_definitions() -> Vec<ToolDef> {
+    vec![
         ToolDef::new("journal_tail",
             "Read the last N journal entries (default 1).",
             json!({"type":"object","properties":{