fix(pi-agent): widen the search options by one property instead of to never

CI caught what I could not check locally: `pnpm exec tsc --noEmit` fails with

    error TS2353: Object literal may only specify known properties,
    and 'source' does not exist in type 'SearchMemoryOptions'.

Adding `source` to SearchMemoryOptions in mem0-ts does not help here. pi-agent
resolves `mem0ai` from npm, so it typechecks against the published 3.1.8 types,
not this repo's source. The declaration still belongs in mem0-ts for the next
release; this call site needs to compile today.

Widened by exactly that one property rather than restoring `as never`, which
was the original objection: a blanket cast also disabled checking of filters,
threshold, topK and rerank on the same literal. `source` reaches the wire
through the SDK's camelToSnakeKeys spread either way.

Verified by installing the package deps and running the real gates: tsc clean,
build clean. vercel-ai-sdk typechecks clean too. Also carries the spool-test
environment fix that had not been committed in this worktree.

Claude-Session: https://claude.ai/code/session_01C7tEmH86HAr7GoAAKCEHZb

integrations/pi-agent-plugin/src/commands.ts

@@ -1,3 +1,4 @@
+import type { SearchMemoryOptions } from "mem0ai";
 import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";
 import type MemoryClient from "mem0ai";
 import type { Mem0Config, ScopeContext, Scope } from "./types.ts";
@@ -34,7 +35,11 @@ export function registerCommands(
       topK: SEARCH_TOP_K,
       rerank: true,
       source: PLATFORM_SOURCE,
-    });
+      // Widened by exactly this one property. `source` reaches the wire via the
+      // SDK's camelToSnakeKeys spread, but it is absent from SearchMemoryOptions
+      // in the published mem0ai types. A blanket `as never` would also disable
+      // checking of filters, threshold, topK and rerank above.
+    } as SearchMemoryOptions & { source: string });
     return result.results ?? [];
   };