docs: document llm.toml and llama-swap metadata discovery

README, CLAUDE.md and .env.example now point at llm.toml for LLM settings
(OPENROUTER_API_KEY stays in env) and describe the legacy env override
window, the discovered picker and the startup cross-check. ADR-0003 records
the move and amends ADR-0002's deployment-config home; CONTEXT.md's
Deployment config / Hard default entries follow. Source comments and the
"set LLAMA_SWAP_URL" error strings name the llm.toml keys.

Also fixes README's AGENTIC_MAX_ITERATIONS default (10 -> 12, what the
code uses).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/reels/mod.rs

@@ -157,7 +157,7 @@ pub enum ScripterMode {
     /// Fast path: single LLM call via the direct client.
     Fast,
     /// Agentic path: resolves the backend through the InsightGenerator
-    /// (honouring LLM_BACKEND, model overrides, etc.). Falls back to
+    /// (honouring llm.toml's backend, model overrides, etc.). Falls back to
     /// Fast on error so a scripting failure never sinks a reel.
     Agentic,
 }
@@ -450,7 +450,7 @@ pub async fn create_reel_handler(
 ) -> impl Responder {
     if app_state.llamacpp.is_none() {
         return HttpResponse::ServiceUnavailable().json(json!({
-            "error": "Reel narration needs the LLM/TTS backend (set LLAMA_SWAP_URL)"
+            "error": "Reel narration needs the LLM/TTS backend (set llamacpp.url in llm.toml)"
         }));
     }