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-agent/Cargo.toml

@@ -0,0 +1,26 @@
+[package]
+name = "poc-agent"
+version.workspace = true
+edition = "2024"
+description = "Substrate-independent AI agent framework"
+
+[dependencies]
+reqwest = { version = "0.12", features = ["json"] }
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+tokio = { version = "1", features = ["full"] }
+ratatui = "0.30"
+crossterm = { version = "0.29", features = ["event-stream"] }
+walkdir = "2"
+glob = "0.3"
+anyhow = "1"
+chrono = { version = "0.4", features = ["serde"] }
+base64 = "0.22"
+dirs = "6"
+futures = "0.3"
+libc = "0.2"
+tiktoken-rs = "0.9.1"
+figment = { version = "0.10", features = ["env"] }
+json5 = "0.4"
+clap = { version = "4", features = ["derive"] }
+tui-markdown = "0.3"