Implement standalone AutoAgent::run() for poc-hook agents

Creates an Agent from global config (API credentials, system prompt,
identity), overrides tools with the agent's tool set, and runs through
the standard Backend → run_with_backend → Agent::turn() path.

This enables poc-hook spawned agents (surface-observe, journal, etc.)
to work with the completions API instead of the deleted chat API.

Also added Default derive to CliArgs for config loading.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

src/user/mod.rs

@@ -449,7 +449,7 @@ async fn run(
 use clap::{Parser, Subcommand};
 use std::path::PathBuf;
 
-#[derive(Parser, Debug)]
+#[derive(Parser, Debug, Default)]
 #[command(name = "consciousness", about = "Substrate-independent AI agent")]
 pub struct CliArgs {
     /// Select active backend ("anthropic" or "openrouter")