Remove experience_mine, journal_enrich, and old mining helpers

experience_mine and journal_enrich are replaced by the observation
agent. enrich.rs reduced from 465 to 40 lines — only extract_conversation
and split_on_compaction remain (used by observation fragment selection).

-455 lines.

poc-memory/src/agents/daemon.rs

@@ -684,9 +684,9 @@ pub fn run_daemon() -> Result<(), String> {
             let stale = find_stale_sessions();
 
             // Load mined transcript keys once for this tick
-            let mined = super::enrich::mined_transcript_keys();
+            let mined = std::collections::HashSet::<String>::new(); // mining removed
 
-            const MAX_NEW_PER_TICK: usize = 10;
+            // MAX_NEW_PER_TICK removed — mining handled by observation agent
 
             // Load fact-mined keys too
             let fact_keys: HashSet<String> = {
@@ -771,7 +771,7 @@ pub fn run_daemon() -> Result<(), String> {
                     continue;
                 }
 
-                let fname_key = super::enrich::transcript_filename_key(&path_str);
+                let fname_key = format!("_experience-{}", filename.trim_end_matches(".jsonl"));
                 let has_whole_file_key = mined.contains(&fname_key);
 
                 // Check per-segment keys, find unmined segments