add chat_as_soul handler for multi-soul rooms

Routes a new event_type "chat_as_soul" through dharma/recv. The Studio
preassembles the system_prompt + transcript and dispatches per-speaker;
the soul-binary just performs the LLM call as the requested speaker_slug.
No engram_compile here — each soul has its own engram (88xx) and the
Studio queries it before composing the prompt.

Also: track the previously-untracked split source modules (chat, routes,
memory, awareness, studio) and add build.sh so the binary can be rebuilt
without the studio’s concat trick. elb resolves the import graph and
emits one .c per .el; we link them together with cc. dist/soul-el now
points at dist/neuron via symlink (matching the launchctl plist).

studio.elh

@@ -0,0 +1,12 @@
+// auto-generated by elc --emit-header - do not edit
+extern fn auth_headers(tok: String) -> Map
+extern fn axon_get(path: String) -> String
+extern fn axon_post(path: String, body: String) -> String
+extern fn handle_conversations(method: String) -> String
+extern fn handle_config(method: String, body: String) -> String
+extern fn dharma_registry() -> String
+extern fn dharma_network_state() -> String
+extern fn handle_dharma(path: String, method: String, body: String) -> String
+extern fn handle_tool(path: String, method: String, body: String) -> String
+extern fn handle_nlg(path: String, method: String, body: String) -> String
+extern fn render_studio() -> String