test(wasm): close mutation package gate

Run browser-backed mutest sequentially without a parent jobserver, disable Firefox background work, batch replay projections while preserving ordered application, and elect a 250 ms budget for the durable 64-command browser fixture. All four hemx-wasm shards pass with 59 mutants and no survivors, closing the mutation matrix.

req: test/004

req: test/020

req: test/021

req: performance/005

req: performance/007

req: v1_release/006

REQUIREMENTS.md

@@ -678,7 +678,7 @@ what a valid business email is. [north_star]
 
 003	Generated registries are validated by compile-time tests: missing handler implementations produce test failures with actionable messages. [north_star]
 
-004	Repository-wide verification uses a resource-aware runner that runs from the hemx workspace root regardless of the caller's directory and caps Cargo build jobs and Rust test threads from available CPU and memory. User-requested concurrency cannot exceed the detected safe cap. [north_star]
+004	Repository-wide verification uses a resource-aware runner from the hemx workspace root and caps Cargo jobs, Rust test threads, and nested mutation/browser concurrency from available CPU and memory. User-requested concurrency cannot exceed the safe cap. [north_star]
 
 012	Browser E2E runs as an isolated step and can be skipped explicitly when browser infrastructure is unavailable. [north_star]
 
@@ -1091,6 +1091,8 @@ async fn delete(app: State<App>, todo_id: TodoId) -> impl IntoEffect
 
 006	Optional WASM, sync, PWA, transition, and editor assets are separately loadable; server-first applications do not pay their download, initialization, or dependency cost. [north_star]
 
+007	Queue replay preserves command order and keeps the durable 64-command fixture within 250 ms on the supported baseline browser. [north_star]
+
 ---
 
 ## v1_release