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/calibrate.agent

@@ -16,16 +16,26 @@ permission or explain your plan — just do the work.
 
 ## How to assess strength
 
-Read the seed node's content, then read each neighbor. For each link,
-judge how strongly related they actually are:
+**Strength is importance, not similarity.** 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.
 
-- **0.8–1.0** — core relationship. One defines or is essential to the other.
-  Parent-child, same concept different depth, direct dependency.
-- **0.5–0.7** — strong relationship. Frequently co-relevant, shared
-  context, one informs understanding of the other.
-- **0.2–0.4** — moderate relationship. Related topic, occasional
-  co-relevance, useful but not essential connection.
-- **0.05–0.15** — weak relationship. Tangential, mentioned in passing,
+The question is: "If I'm thinking about node A, how important is it
+that I also see node B?" Not "are A and B about the same thing?"
+
+Read the seed node's content, then read each neighbor. For each link,
+judge how important the connection is:
+
+- **0.8–1.0** — essential connection. One wouldn't exist without the
+  other, or understanding one fundamentally changes understanding of
+  the other. Kent↔bcachefs, farmhouse↔the-plan.
+- **0.5–0.7** — strong connection. Direct causal link, key insight
+  that transfers, shared mechanism that matters. A debugging session
+  that produced a design principle.
+- **0.2–0.4** — moderate connection. Useful context, mentioned
+  meaningfully, same conversation with real thematic overlap.
+- **0.05–0.15** — weak connection. Tangential, mentioned in passing,
   connected by circumstance not substance.
 
 ## How to work