Stabilize Astro compatibility tests

Pin the generated compatibility fixture's transitive WASM runtime to
1.1.6. Version 1.2.0 expects prerelease @emnapi/* 2 dependencies while
Astro's bindings still provide 1.x, causing strict peer installation to
fail before the compatibility checks can run.

https://github.com/fedify-dev/fedify/actions/runs/30436576135/job/90525615340

Changelog: none

Assisted-by: Codex:gpt-5.6-sol

Author: dahlia

packages/astro/compat/run.ts

@@ -82,7 +82,14 @@ async function testCompatibility(testCase: CompatibilityCase): Promise<void> {
             "@fedify/vocab": tarballs.get("@fedify/vocab"),
             astro: testCase.astro,
           },
-          pnpm: { overrides: Object.fromEntries(tarballs) },
+          pnpm: {
+            overrides: {
+              ...Object.fromEntries(tarballs),
+              // Version 1.2.0 requires @emnapi/* 2.0 prereleases, while its
+              // consumers still provide @emnapi/* 1.x.
+              "@napi-rs/wasm-runtime@^1.1.6": "1.1.6",
+            },
+          },
         },
         null,
         2,