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/openrouter.rs

@@ -26,7 +26,7 @@ const CACHE_DURATION_SECS: u64 = 15 * 60;
 /// Default completion cap sent as `max_tokens`. OpenRouter pre-authorizes
 /// credit against the requested max (defaulting to the model's full output
 /// window when omitted), so expensive models fail with credit-limit errors
-/// even when the actual reply is short. Override via `OPENROUTER_MAX_TOKENS`.
+/// even when the actual reply is short. Override via `openrouter.max_tokens`.
 pub const DEFAULT_MAX_TOKENS: u32 = 16384;
 
 #[derive(Clone)]