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/src/cli.rs

@@ -0,0 +1,71 @@
+// cli.rs — Command-line argument parsing
+//
+// All fields are Option<T> so unset args don't override config file
+// values. The layering order is:
+//   defaults < config file < CLI args
+//
+// Subcommands:
+//   (none)        Launch the TUI agent
+//   read          Print new output since last check and exit
+//   write <msg>   Send a message to the running agent
+
+use clap::{Parser, Subcommand};
+use std::path::PathBuf;
+
+#[derive(Parser, Debug)]
+#[command(name = "poc-agent", about = "Substrate-independent AI agent")]
+pub struct CliArgs {
+    /// Select active backend ("anthropic" or "openrouter")
+    #[arg(long)]
+    pub backend: Option<String>,
+
+    /// Model override
+    #[arg(short, long)]
+    pub model: Option<String>,
+
+    /// API key override
+    #[arg(long)]
+    pub api_key: Option<String>,
+
+    /// Base URL override
+    #[arg(long)]
+    pub api_base: Option<String>,
+
+    /// Enable debug logging
+    #[arg(long)]
+    pub debug: bool,
+
+    /// Print effective config with provenance and exit
+    #[arg(long)]
+    pub show_config: bool,
+
+    /// Override all prompt assembly with this file
+    #[arg(long)]
+    pub system_prompt_file: Option<PathBuf>,
+
+    /// Project memory directory
+    #[arg(long)]
+    pub memory_project: Option<PathBuf>,
+
+    /// Max consecutive DMN turns
+    #[arg(long)]
+    pub dmn_max_turns: Option<u32>,
+
+    #[command(subcommand)]
+    pub command: Option<SubCmd>,
+}
+
+#[derive(Subcommand, Debug)]
+pub enum SubCmd {
+    /// Print new output since last read and exit
+    Read {
+        /// Stream output continuously instead of exiting
+        #[arg(short, long)]
+        follow: bool,
+    },
+    /// Send a message to the running agent
+    Write {
+        /// The message to send
+        message: Vec<String>,
+    },
+}