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/ai/handlers.rs

@@ -1089,7 +1089,7 @@ pub struct OpenRouterModelsResponse {
 
 /// GET /insights/openrouter/models - Curated OpenRouter model ids exposed
 /// to clients for the hybrid backend. Returned verbatim from
-/// `OPENROUTER_ALLOWED_MODELS`; no live call to OpenRouter.
+/// `openrouter.allowed`; no live call to OpenRouter.
 #[get("/insights/openrouter/models")]
 pub async fn get_openrouter_models_handler(
     _claims: Claims,