[instructions] Sync instruction files with release v0.83.1

.github/aw/syntax-agentic.md

@@ -26,7 +26,7 @@ description: Agentic workflow specific frontmatter fields for GitHub Agentic Wor
 - **`max-runs:`** - Deprecated legacy alias for the AWF invocation cap (`apiProxy.maxRuns`, defaults to `500` when omitted). Use `max-turns` instead; run `gh aw fix` to migrate.
 - **`max-ai-credits:`** - Per-run AI Credits (AIC) budget enforced by the AWF firewall (integer or `K`/`M` short-form string like `100M`; default `1000`). Set a negative value to disable enforcement and token steering. See [token-optimization.md](token-optimization.md).
 - **`max-turn-cache-misses:`** - Maximum consecutive AWF cache misses allowed before the API proxy blocks further requests (integer, default `5`). Maps to `apiProxy.maxCacheMisses`; precedence is frontmatter → `GH_AW_DEFAULT_MAX_TURN_CACHE_MISSES` env override → built-in default.
-- **`models:`** - Model policy and optional pricing (object). Experimental policy fields `allowed` / `blocked` (lists of model names or patterns) restrict which models the workflow may use; they map to AWF `apiProxy.allowedModels` / `disallowedModels` and merge as unions across imports. Environment-variable overrides are supported. The separate `providers` field supplies custom pricing (see [token-optimization.md](token-optimization.md)).
+- **`models:`** - Model policy and optional pricing (object). Experimental policy fields `allowed` / `blocked` (lists of model names or patterns) restrict which models the workflow may use; they map to AWF `apiProxy.allowedModels` / `disallowedModels` and merge as unions across imports. Environment-variable overrides are supported. The separate `providers` field supplies custom pricing, and `default-ai-credits-pricing` (`input`/`output` in $/1M tokens) is a fallback rate for models absent from the built-in table — required to avoid HTTP 400 rejections for self-hosted/BYOK models (set both to `0` for free/local models). See [token-optimization.md](token-optimization.md).
 
   ```yaml
   models:

.github/aw/token-optimization.md

@@ -381,6 +381,8 @@ max-daily-ai-credits: 500M  # per-user 24h cap; -1 disables
 
 For custom or private models, the top-level **`models:`** frontmatter field supplies pricing in the same structure as `models.json` (keyed `providers.<provider>.models.<model>.cost` with `input`/`output`/`cache_read`/`cache_write` per-token costs). Entries are merged with the built-in `models.json` at runtime — they override matching models and fill gaps for unknown ones — so AI Credit accounting stays accurate for models gh-aw does not price by default.
 
+For self-hosted or BYOK models absent from the built-in table (e.g. Ollama, vLLM), set **`models.default-ai-credits-pricing`** (`input`/`output` in $/1M tokens, both `0` for free/local models); without it the AWF proxy rejects unrecognized models with HTTP 400 `unknown_model_ai_credits`.
+
 ---
 
 ## Additional Resources