sanitize mcp schemas for Gemini; fix gpt-codex-mini alias; add matrix filter

Gemini's generateContent API rejects arktype's `{anyOf:[{enum:[...]}]}` string-enum
encoding, `$schema` metadata, and `anyOf` with sibling fields. Port the old
sanitizer back as an isolated module (action/mcp/geminiSanitizer.ts) and gate it
on `isGeminiRouted(ctx)` so non-gemini routes see the original schema. Wires
`resolvedModel` onto ToolContext so the sanitizer can see the upstream specifier.

Also bumps `openai/gpt-codex-mini` alias from the deprecated `codex-mini-latest`
to `gpt-5.1-codex-mini`, matching the openrouter resolve.

Adds a `filter` workflow_dispatch input + MATRIX_FILTER env that restricts the
models-live matrix to aliases matching a substring, so we can iterate on a
single provider (e.g. `filter=gemini`) without paying to run every model.

mcp/shared.ts

@@ -2,6 +2,7 @@ import type { StandardSchemaV1 } from "@standard-schema/spec";
 import { encode as toonEncode } from "@toon-format/toon";
 import type { FastMCP, Tool } from "fastmcp";
 import { formatJsonValue, log } from "../utils/cli.ts";
+import { isGeminiRouted, sanitizeToolForGemini } from "./geminiSanitizer.ts";
 import type { ToolContext } from "./server.ts";
 
 export const tool = <const params>(
@@ -61,9 +62,10 @@ export const execute = <T, R extends Record<string, any> | string>(
   return _fn;
 };
 
-export const addTools = (_ctx: ToolContext, server: FastMCP<any>, tools: Tool<any, any>[]) => {
+export const addTools = (ctx: ToolContext, server: FastMCP<any>, tools: Tool<any, any>[]) => {
+  const shouldSanitize = isGeminiRouted(ctx);
   for (const tool of tools) {
-    server.addTool(tool);
+    server.addTool(shouldSanitize ? sanitizeToolForGemini(tool) : tool);
   }
   return server;
 };