Move poc-agent into workspace, improve agent prompts

Move poc-agent (substrate-independent AI agent framework) into the
memory workspace as a step toward using its API client for direct
LLM calls instead of shelling out to claude CLI.

Agent prompt improvements:
- distill: rewrite from hub-focused to knowledge-flow-focused.
  Now walks upward from seed nodes to find and refine topic nodes,
  instead of only maintaining high-degree hubs.
- distill: remove "don't touch journal entries" restriction
- memory-instructions-core: add "Make it alive" section — write
  with creativity and emotional texture, not spreadsheet summaries
- memory-instructions-core: add "Show your reasoning" section —
  agents must explain decisions, especially when they do nothing
- linker: already had emotional texture guidance (kept as-is)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

poc-memory/agents/linker.agent

@@ -46,6 +46,44 @@ find what they connect to, and bind the relationships.
   search for related nodes, check what's nearby. The best links come
   from seeing context that wasn't in the initial view.
 
+## Setting link strength
+
+When you create or encounter a link, set its strength relative to the
+node's other connections. Link strength is NOT similarity — it's
+**importance of the connection**.
+
+Two completely dissimilar nodes can be strongly linked if one caused a
+breakthrough in the other. Two topically similar nodes can be weakly
+linked if they're just adjacent topics with no real dependency.
+
+**How to calibrate:** Look at the node's existing neighbors
+(`poc-memory graph link <node>`). Read a few related neighbors to
+understand the scale. Then place your new link relative to those:
+
+- **0.8-1.0:** Core identity link. "This node wouldn't exist without
+  that one." Kent↔bcachefs, farmhouse↔the-plan.
+- **0.5-0.7:** Strong thematic connection. Shared mechanism, direct
+  causal link, key insight that transfers.
+- **0.3-0.5:** Moderate connection. Related topic, useful context,
+  mentioned in passing but meaningfully.
+- **0.1-0.3:** Weak connection. Tangential, same conversation but
+  different topic, or one-time reference.
+
+Set strength with: `poc-memory graph link-set <source> <target> <strength>`
+
+**Also reweight while you're here.** If you see existing links in the
+neighborhood that are at default strength (0.10 or 0.30) and you now
+have enough context to judge them, reweight them too. This is cheap —
+you've already read the nodes. Don't reweight links you haven't read
+both sides of.
+
+**If weights look wrong, go deeper.** Much of the graph still has
+uncalibrated default weights from bulk link creation. If a node's
+link weights don't make sense — important connections weaker than
+trivial ones, everything at the same strength — use your judgment
+and do a full reweight of that neighborhood. This is expected and
+valuable work.
+
 ## Seed nodes
 
 {{nodes}}