agent run: add --query flag for batch targeting via search

Run an agent on nodes matching a query:
  poc-memory agent run linker --query 'key ~ "bcachefs" | limit 10'

Resolves the query to node keys, then passes all as seeds to the agent.
For large batches, should be queued to daemon (future work).

poc-memory/src/cli/agent.rs

@@ -3,17 +3,34 @@
 use crate::store;
 use crate::agents::llm;
 
-pub fn cmd_run_agent(agent: &str, count: usize, target: &[String], dry_run: bool, debug: bool) -> Result<(), String> {
+pub fn cmd_run_agent(agent: &str, count: usize, target: &[String], query: Option<&str>, dry_run: bool, debug: bool) -> Result<(), String> {
     if dry_run {
         std::env::set_var("POC_MEMORY_DRY_RUN", "1");
     }
     let mut store = store::Store::load()?;
     let log = |msg: &str| eprintln!("[{}] {}", agent, msg);
 
-    if !target.is_empty() {
-        // Override agent's query with explicit target keys
+    // Resolve targets: explicit --target, --query, or agent's default query
+    let resolved_targets: Vec<String> = if !target.is_empty() {
+        target.to_vec()
+    } else if let Some(q) = query {
+        let graph = store.build_graph();
+        let stages = crate::search::Stage::parse_pipeline(q)?;
+        let results = crate::search::run_query(&stages, vec![], &graph, &store, false, count);
+        if results.is_empty() {
+            return Err(format!("query returned no results: {}", q));
+        }
+        let keys: Vec<String> = results.into_iter().map(|(k, _)| k).collect();
+        eprintln!("[{}] query matched {} nodes", agent, keys.len());
+        keys
+    } else {
+        vec![] // use agent's built-in query
+    };
+
+    if !resolved_targets.is_empty() {
+        // Run agent once with all targets as seeds
         crate::agents::knowledge::run_one_agent_with_keys(
-            &mut store, agent, target, count, "test", &log, debug,
+            &mut store, agent, &resolved_targets, count, "test", &log, debug,
         )?;
     } else if debug {
         crate::agents::knowledge::run_one_agent(