feat: replace generic personas with Solo, Ralph, Scout, and Reviewer (#203)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

desktop/scripts/check-file-sizes.mjs

@@ -30,6 +30,7 @@ const rules = [
 
 // Exceptions should stay rare and temporary. Prefer splitting files instead.
 const overrides = new Map([
+  ["src-tauri/src/managed_agents/personas.rs", 600], // built-in persona system prompts (Solo, Ralph, Strategist) are long string literals
   ["src-tauri/src/managed_agents/persona_card.rs", 772], // PNG/ZIP persona card codec + provider/model fields + 27 unit tests (~350 lines of tests); rustfmt adds line breaks around long literals/builders
   ["src/app/AppShell.tsx", 810], // message edit state + handlers + ChannelPane edit prop threading
   ["src/features/channels/hooks.ts", 550], // canvas query + mutation hooks + DM hide mutation

desktop/src-tauri/src/managed_agents/mod.rs

@@ -1,5 +1,6 @@
 mod backend;
 mod discovery;
+mod persona_avatars;
 mod persona_card;
 mod personas;
 mod runtime;