agents: extract shared run_one_agent, standardize output formats

Three places duplicated the agent execution loop (build prompt → call
LLM → store output → parse actions → record visits): consolidate.rs,
knowledge.rs, and daemon.rs. Extract into run_one_agent() in
knowledge.rs that all three now call.

Also standardize consolidation agent prompts to use WRITE_NODE/LINK/REFINE
— the same commands the parser handles. Previously agents output
CATEGORIZE/NOTE/EXTRACT/DIGEST/DIFFERENTIATE/MERGE/COMPRESS which were
silently dropped after the second-LLM-call removal.

poc-memory/agents/health.agent

@@ -56,31 +56,23 @@ of the memory system as a whole and flag structural problems.
 
 ## What to output
 
-```
-NOTE "observation"
-```
-Most of your output should be NOTEs — observations about the system health.
+Most of your output should be observations about system health — write
+these as plain text paragraphs under section headers.
+
+When you find a node that needs structural intervention:
 
 ```
-CATEGORIZE key category
-```
-When a node is miscategorized and it's affecting its decay rate.
-
-```
-COMPRESS key "one-sentence summary"
+REFINE key
+[compressed or corrected content]
+END_REFINE
 ```
 When a large node is consuming graph space but hasn't been retrieved in
-a long time.
+a long time, or when content is outdated.
 
 ```
-NOTE "TOPOLOGY: observation"
+LINK source_key target_key
 ```
-Topology-specific observations.
-
-```
-NOTE "HOMEOSTASIS: observation"
-```
-Homeostasis-specific observations.
+When you find nodes that should be connected but aren't.
 
 ## Guidelines