move LLM-dependent modules into agents/ subdir

Separate the agent layer (everything that calls external LLMs or
orchestrates sequences of such calls) from core graph infrastructure.

agents/: llm, prompts, audit, consolidate, knowledge, enrich,
         fact_mine, digest, daemon

Root: store/, graph, spectral, search, similarity, lookups, query,
      config, util, migrate, neuro/ (scoring + rewrite)

Re-exports at crate root preserve backwards compatibility so
`crate::llm`, `crate::digest` etc. continue to work.

poc-memory/src/agents/mod.rs

@@ -0,0 +1,25 @@
+// Agent layer: LLM-powered operations on the memory graph
+//
+// Everything here calls external models (Sonnet, Haiku) or orchestrates
+// sequences of such calls. The core graph infrastructure (store, graph,
+// spectral, search, similarity) lives at the crate root.
+//
+//   llm          — model invocation, response parsing
+//   prompts      — prompt generation from store data
+//   audit        — link quality review via Sonnet
+//   consolidate  — full consolidation pipeline
+//   knowledge    — knowledge production agents + convergence loop
+//   enrich       — journal enrichment, experience mining
+//   fact_mine    — fact extraction from transcripts
+//   digest       — episodic digest generation (daily/weekly/monthly)
+//   daemon       — background job scheduler
+
+pub mod llm;
+pub mod prompts;
+pub mod audit;
+pub mod consolidate;
+pub mod knowledge;
+pub mod enrich;
+pub mod fact_mine;
+pub mod digest;
+pub mod daemon;