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/store/types.rs

@@ -133,10 +133,15 @@ pub fn epoch_to_local(epoch: i64) -> (i32, u32, u32, u32, u32, u32) {
         chrono::LocalResult::Single(dt) => dt,
         chrono::LocalResult::Ambiguous(dt, _) => dt,
         chrono::LocalResult::None => {
-            // DST gap — add an hour to land in valid local time
+            // DST gap or invalid — try shifting, then fall back to UTC
             Local.timestamp_opt(epoch + 3600, 0)
                 .earliest()
-                .unwrap_or_else(|| chrono::Utc.timestamp_opt(epoch, 0).unwrap().with_timezone(&Local))
+                .or_else(|| chrono::Utc.timestamp_opt(epoch, 0).earliest()
+                    .map(|dt| dt.with_timezone(&Local)))
+                .unwrap_or_else(|| {
+                    // Completely invalid timestamp — use epoch 0
+                    chrono::Utc.timestamp_opt(0, 0).unwrap().with_timezone(&Local)
+                })
         }
     };
     (