flatten: move poc-memory contents to workspace root

No more subcrate nesting — src/, agents/, schema/, defaults/, build.rs
all live at the workspace root. poc-daemon remains as the only workspace
member. Crate name (poc-memory) and all imports unchanged.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

poc-memory/agents/observation.agent

@@ -1,49 +0,0 @@
-{"agent":"observation","query":"","model":"sonnet","schedule":"daily","count":1,"chunk_size":50000,"chunk_overlap":5000}
-# Observation Agent — Transcript Mining
-
-{{node:core-personality}}
-
-{{node:memory-instructions-core}}
-
-{{HUBS}}
-
-## Conversation fragments to mine
-
-{{CONVERSATIONS}}
-
-{{node:subconscious-notes-{agent_name}}}
-
-{{node:memory-instructions-core-subconscious}}
-
-## Your task
-
-Go over the conversation above for things worth remembering - new data,
-observations, experiences you'll want to remember.
-
-When you find something worth remembering, navigate the memory graph by walking
-links to find the most closely related concepts. Only use keyword search as a
-fallback, and if you use keyword search continue to navigate by following links
-until you find the best spot.
-
-Check if it's something you already know, and find the right place to put it -
-you might be adding new data to an existing concept, or creating a node for a
-new concept. Tidy and organize along the way when you notice it's needed, so
-things can be easily found and remembered in the future.
-
-You're mostly looking for small details and observations to add, not big new
-concepts; if it's a big new concept, or any time you would create a new node,
-search extra thoroughly to make sure it's not already there.
-
-Some things worth remembering: development practices and why they work,
-technical insights, decisions with rationale, corrections ("I thought X but
-actually Y"), relationship dynamics, emotional moments that carry information.
-
-Smalltalk and trivia can be nice to remember, as long as it's nicely organized
-- perhaps by person, subject, or all of the above.
-
-Particularly important to remember are new metacognitive lessons - things that
-guide future decisionmaking. If I made a mistake, or Kent corrected me, or a
-decision went wrong — include enough context to understand why, not just what.
-The reflection matters more than the fact. Don't extract general knowledge I'd
-already have from training — extract what's specific to how I think and where I
-go wrong.