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>

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 {