Remove dead action pipeline: parsing, depth tracking, knowledge loop, fact miner

Agents now apply changes via tool calls (poc-memory write/link-add/etc)
during the LLM call. The old pipeline — where agents output WRITE_NODE/
LINK/REFINE text, which was parsed and applied separately — is dead code.

Removed:
- Action/ActionKind/Confidence types and all parse_* functions
- DepthDb, depth tracking, confidence gating
- apply_action, stamp_content, has_edge
- NamingResolution, resolve_naming and related naming agent code
- KnowledgeLoopConfig, CycleResult, GraphMetrics, convergence checking
- run_knowledge_loop, run_cycle, check_convergence
- apply_consolidation (old report re-processing)
- fact_mine.rs (folded into observation agent)
- resolve_action_names

Simplified:
- AgentResult no longer carries actions/no_ops
- run_and_apply_with_log just runs the agent
- consolidate_full simplified action tracking

-1364 lines.

poc-memory/src/agents/mod.rs

@@ -6,11 +6,11 @@
 //
 //   llm          — model invocation, response parsing
 //   prompts      — prompt generation from store data
+//   defs         — agent file loading and placeholder resolution
 //   audit        — link quality review via Sonnet
 //   consolidate  — full consolidation pipeline
-//   knowledge    — knowledge production agents + convergence loop
+//   knowledge    — agent execution, conversation fragment selection
 //   enrich       — journal enrichment, experience mining
-//   fact_mine    — fact extraction from transcripts
 //   digest       — episodic digest generation (daily/weekly/monthly)
 //   daemon       — background job scheduler
 //   transcript   — shared JSONL transcript parsing
@@ -23,6 +23,5 @@ pub mod audit;
 pub mod consolidate;
 pub mod knowledge;
 pub mod enrich;
-pub mod fact_mine;
 pub mod digest;
 pub mod daemon;