agents: extract run_and_apply, eliminate dead split-plan.md

- Add run_and_apply() — combines run_one_agent + action application
  into one call. Used by daemon job_consolidation_agent and
  consolidate_full, which had identical run+apply loops.

- Port split_plan_prompt() to use split.agent via defs::resolve_placeholders
  instead of loading the separate split-plan.md template. Make
  resolve_placeholders public for this.

- Delete prompts/split-plan.md — superseded by agents/split.agent
  which was already the canonical definition.

poc-memory/src/agents/knowledge.rs

@@ -332,6 +332,26 @@ pub struct AgentResult {
     pub node_keys: Vec<String>,
 }
 
+/// Run a single agent and apply its actions (no depth tracking).
+///
+/// Returns (total_actions, applied_count) or an error.
+pub fn run_and_apply(
+    store: &mut Store,
+    agent_name: &str,
+    batch_size: usize,
+    llm_tag: &str,
+) -> Result<(usize, usize), String> {
+    let result = run_one_agent(store, agent_name, batch_size, llm_tag)?;
+    let ts = store::compact_timestamp();
+    let mut applied = 0;
+    for action in &result.actions {
+        if apply_action(store, action, agent_name, &ts, 0) {
+            applied += 1;
+        }
+    }
+    Ok((result.actions.len(), applied))
+}
+
 /// Run a single agent: build prompt → call LLM → store output → parse actions → record visits.
 ///
 /// This is the common pipeline shared by the knowledge loop, consolidation pipeline,