Upgrade workspace to edition 2024, add --local flag to agent run

Edition 2024 changes:
- gen is reserved: rename variable in query/engine.rs
- set_var is unsafe: wrap in unsafe block in cli/agent.rs
- match ergonomics: add explicit & in spectral.rs filter closure

New --local flag for `poc-memory agent run` bypasses the daemon and
runs the agent directly in-process. Useful for testing agent prompt
changes without waiting in the daemon queue.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

poc-memory/src/spectral.rs

@@ -474,7 +474,7 @@ pub fn analyze_positions(
             let coords = &emb.coords[&key];
 
             let (nearest_community, dist_to_nearest) = centers.iter()
-                .filter(|(&c, _)| c != comm)
+                .filter(|&(&c, _)| c != comm)
                 .map(|(&c, center)| (c, weighted_distance(coords, center, &weights)))
                 .min_by(|a, b| a.1.total_cmp(&b.1))
                 .unwrap_or((comm, f64::MAX));