test: restore 100% coverage on root src/ (errors.ts + pool.ts defensive guards)

src/errors.ts

@@ -174,6 +174,8 @@ function getErrorMessage(errno: number): string {
     return `Unknown LZMA error code: ${errno}`;
   }
   const msg = messages[errno];
+  /* v8 ignore start: defensive after bounds check on L172 — errno always in [0, messages.length) here */
   if (msg === undefined) return `Unknown LZMA error code: ${errno}`;
+  /* v8 ignore stop */
   return msg;
 }

src/pool.ts

@@ -165,13 +165,15 @@ export class LZMAPool extends EventEmitter {
     }
 
     const item = this.queue.shift();
+    /* v8 ignore start: defensive after queue.length > 0 guard on L163 — shift() always returns a value here */
     if (item === undefined) {
       // The `this.queue.length === 0` early-return guard above means shift()
       // must return a value here. Returning silently would let queued tasks
       // stall on a future invariant breach (re-entrancy, refactor, etc.).
       // Throw so the bug surfaces at the breach instead of as a hung pool.
       throw new Error('Invariant violation: queue was non-empty but shift() returned undefined');
     }
+    /* v8 ignore stop */
 
     this.metrics.active++;
     this.metrics.queued = this.queue.length;