rename agent: LLM-powered semantic key generation for memory nodes

New consolidation agent that reads node content and generates semantic
3-5 word kebab-case keys, replacing auto-generated slugs (5K+ journal
entries with truncated first-line slugs, 2.5K mined transcripts with
opaque UUIDs).

Implementation:
- prompts/rename.md: agent prompt template with naming conventions
- prompts.rs: format_rename_candidates() selects nodes with long
  auto-generated keys, newest first
- daemon.rs: job_rename_agent() parses RENAME actions from LLM
  output and applies them directly via store.rename_node()
- Wired into RPC handler (run-agent rename) and TUI agent types
- Fix epoch_to_local panic on invalid timestamps (fallback to UTC)

Rename dramatically improves search: key-component matching on
"journal#2026-02-28-violin-dream-room" makes the node findable by
"violin", "dream", or "room" — the auto-slug was unsearchable.

poc-memory/src/tui.rs

@@ -32,7 +32,7 @@ const POLL_INTERVAL: Duration = Duration::from_secs(2);
 // Agent types we know about, in display order
 const AGENT_TYPES: &[&str] = &[
     "health", "replay", "linker", "separator", "transfer",
-    "apply", "orphans", "cap", "digest", "digest-links", "knowledge",
+    "apply", "orphans", "cap", "digest", "digest-links", "knowledge", "rename",
 ];
 
 fn status_sock_path() -> PathBuf {