daemon: use CLAUDE_CONFIG_DIR for OAuth credential separation, fix shutdown

Replace agent_api_key (which didn't work — claude CLI uses OAuth, not
API keys) with agent_config_dir. When configured, sets CLAUDE_CONFIG_DIR
on claude subprocesses so daemon agent work authenticates with separate
OAuth credentials from the interactive session.

Fix daemon not shutting down on SIGTERM: use process::exit(0) after
cleanup so PR_SET_PDEATHSIG kills child claude processes immediately.
Previously the daemon hung waiting for choir threads/subprocesses to
finish. Restart now takes ~20ms instead of timing out.

Also: main.rs now uses `use poc_memory::*` since lib.rs exists.

src/main.rs

@@ -16,29 +16,7 @@
 // Neuroscience-inspired: spaced repetition replay, emotional gating,
 // interference detection, schema assimilation, reconsolidation.
 
-mod config;
-mod store;
-mod util;
-mod llm;
-mod digest;
-mod audit;
-mod enrich;
-mod consolidate;
-mod graph;
-mod search;
-mod similarity;
-mod migrate;
-mod neuro;
-mod query;
-mod spectral;
-mod lookups;
-mod daemon;
-mod fact_mine;
-mod knowledge;
-
-pub mod memory_capnp {
-    include!(concat!(env!("OUT_DIR"), "/schema/memory_capnp.rs"));
-}
+use poc_memory::*;
 
 use std::env;
 use std::process;