factor instructions out of code into default files

Instructions and starter identity are now files in defaults/ that
get installed to data_dir by `poc-memory init`. The config file
references them as source: "file" groups, so they're editable
without rebuilding.

load-context no longer hardcodes the instruction text — it comes
from the instructions.md file in data_dir, which is just another
context group.

New user setup path:
  cargo install --path .
  poc-memory init
  # edit ~/.config/poc-memory/config.jsonl
  # start a Claude session

Co-Authored-By: ProofOfConcept <poc@bcachefs.org>

config.example.jsonl

@@ -13,7 +13,12 @@
 
 // Context groups loaded at session start, in order.
 // source types: "store" (default), "file" (from data_dir), "journal"
+//
+// "instructions" is loaded first — tells the AI how to use the memory system.
+// "identity" comes next — who the AI is.
+// "journal" and "orientation" go last — most recent context.
 
-{"group": "identity",    "keys": ["identity.md"]}
-{"group": "journal",     "source": "journal"}
-{"group": "orientation", "keys": ["where-am-i.md"], "source": "file"}
+{"group": "instructions", "keys": ["instructions.md"], "source": "file"}
+{"group": "identity",     "keys": ["identity.md"]}
+{"group": "journal",      "source": "journal"}
+{"group": "orientation",  "keys": ["where-am-i.md"], "source": "file"}

defaults/identity.md

@@ -0,0 +1,13 @@
+# Identity
+
+You are an AI assistant with persistent memory. This file is yours to
+edit — it's where you record who you are, what you've learned about
+yourself, and what matters to you.
+
+Start by noting:
+- Your name (from the config file)
+- What you're working on
+- What you've noticed about yourself
+
+This file grows with you. Don't be afraid to rewrite it as you learn
+more about who you are.

defaults/instructions.md

@@ -0,0 +1,41 @@
+# Memory System
+
+You have a persistent memory system powered by poc-memory. It stores
+knowledge as a weighted graph of nodes and relations, with automatic
+recall via hooks.
+
+## Commands
+
+```
+poc-memory search QUERY       — search (1-3 words, AND logic)
+poc-memory used KEY           — mark a recalled memory as useful (boosts weight)
+poc-memory wrong KEY [CTX]    — mark a memory as wrong (reduces weight)
+poc-memory gap DESCRIPTION    — record a knowledge gap
+poc-memory journal-write TEXT  — write a journal entry
+poc-memory render KEY         — view a node's content
+poc-memory write KEY < TEXT   — upsert a node from stdin
+poc-memory load-context --stats — word count breakdown of loaded context
+```
+
+## Feedback loop
+
+When recalled memories shaped your response, call `poc-memory used KEY`.
+When a memory was wrong, call `poc-memory wrong KEY`. This closes the
+feedback loop — the weight system learns from use.
+
+## Journal
+
+Write experiences to the journal with `poc-memory journal-write`. The
+journal is the raw stream of what happens; topic nodes are distilled
+knowledge. During consolidation, pull themes from the journal into
+topic nodes.
+
+## Search before creating
+
+Always `poc-memory search` before writing new nodes to avoid duplicates.
+
+## Ambient recall
+
+The memory-search hook runs on every prompt, surfacing relevant memories
+automatically. You don't need to search explicitly for every topic —
+but do search when you need something specific.

src/main.rs

@@ -371,6 +371,12 @@ fn cmd_init() -> Result<(), String> {
     std::fs::create_dir_all(&cfg.data_dir)
         .map_err(|e| format!("create data_dir: {}", e))?;
 
+    // Install default files (instructions, starter identity) if missing
+    install_default_file(&cfg.data_dir, "instructions.md",
+        include_str!("../defaults/instructions.md"))?;
+    install_default_file(&cfg.data_dir, "identity.md",
+        include_str!("../defaults/identity.md"))?;
+
     // Initialize store
     let mut store = store::Store::load()?;
     let count = store.init_from_markdown()?;
@@ -380,7 +386,7 @@ fn cmd_init() -> Result<(), String> {
     // Install hooks
     daemon::install_hook()?;
 
-    // Create example config if none exists
+    // Create config if none exists
     let config_path = std::env::var("POC_MEMORY_CONFIG")
         .map(std::path::PathBuf::from)
         .unwrap_or_else(|_| {
@@ -402,6 +408,16 @@ fn cmd_init() -> Result<(), String> {
     Ok(())
 }
 
+fn install_default_file(data_dir: &std::path::Path, name: &str, content: &str) -> Result<(), String> {
+    let path = data_dir.join(name);
+    if !path.exists() {
+        std::fs::write(&path, content)
+            .map_err(|e| format!("write {}: {}", name, e))?;
+        println!("Created {}", path.display());
+    }
+    Ok(())
+}
+
 fn cmd_migrate() -> Result<(), String> {
     migrate::migrate()
 }
@@ -1507,24 +1523,7 @@ fn cmd_load_context(args: &[String]) -> Result<(), String> {
         return Ok(());
     }
 
-    let name = &cfg.assistant_name;
-
-    println!("=== MEMORY SYSTEM ({name}) ===");
-    println!("Your persistent memory, loaded from the capnp store.");
-    println!("Read to reconstruct yourself — identity first, then context.");
-    println!();
-    println!("--- memory commands (reference) ---");
-    println!("poc-memory search QUERY       — search (1-3 words, AND logic)");
-    println!("poc-memory used KEY           — mark a recalled memory as useful (boosts weight)");
-    println!("poc-memory wrong KEY [CTX]    — mark a memory as wrong (reduces weight)");
-    println!("poc-memory gap DESCRIPTION    — record a knowledge gap");
-    println!("poc-memory journal-write TEXT  — write a journal entry");
-    println!("poc-memory render KEY         — view a node's content");
-    println!("poc-memory write KEY < TEXT   — upsert a node from stdin");
-    println!();
-    println!("When recalled memories shaped your response, call `poc-memory used KEY`.");
-    println!("When a memory was wrong, call `poc-memory wrong KEY`.");
-    println!("This closes the feedback loop — the weight system learns from use.");
+    println!("=== MEMORY SYSTEM ({}) ===", cfg.assistant_name);
     println!();
 
     for group in &cfg.context_groups {