test(vitest): run pool workers with the WASM runtime flags (#1779) (#2046)

A vitest pool worker is the one launch path that never received
`--liftoff-only`, so the suite compiled tree-sitter grammars on the
turboshaft tier. Once ~640 extraction tests have warmed a grammar function
up, its background tier-up job (Turboshaft LoopUnrollingPhase, symbolized
from the native stack) exhausts a compiler Zone and aborts the worker:
`Fatal process out of memory: Zone`, which vitest reports only as "Worker
exited unexpectedly" with the file's remaining tests unrun.

Pass WASM_RUNTIME_FLAGS through poolOptions.forks.execArgv, so the test
process matches the bundled launcher, the CLI re-exec and refresh-launcher.
V8 flags are process-global, so parse worker threads are covered too.

Linux x64, Node 24.15, `__tests__/extraction.test.ts` (655 tests):
without the flag 3 of 4 runs died at the same test (639 passed);
with it 2 of 2 passed, in 19–24s instead of 34–41s. Neither
`--no-wasm-loop-unrolling` nor `--no-wasm-dynamic-tiering` prevents it.


(cherry picked from commit 565ec815e6)

Co-authored-by: danusha2345 <danusha2345@users.noreply.github.com>
Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

vitest.config.mts

@@ -1,4 +1,5 @@
 import { defineConfig } from 'vitest/config';
+import { WASM_RUNTIME_FLAGS } from './src/extraction/wasm-runtime-flags';
 
 /**
  * The SHARED base. `vitest.workspace.mts` extends it twice — once for the
@@ -36,6 +37,21 @@ export default defineConfig({
        */
       CODEGRAPH_TELEMETRY: '0',
     },
+    /**
+     * The same V8 flags every real launch path passes (the bundled launcher,
+     * the CLI's self re-exec, refresh-launcher): keep tree-sitter grammar
+     * compilation on the Liftoff baseline tier. Without them a pool worker
+     * runs the grammars on the turboshaft optimizing tier, and once enough
+     * parses have warmed a grammar function up, its background tier-up job
+     * exhausts a compiler Zone and aborts the worker — `Fatal process out of
+     * memory: Zone`, surfaced by vitest only as "Worker exited unexpectedly"
+     * with the rest of the file's tests silently unrun (#1779; the product-side
+     * story is in wasm-runtime-flags.ts, #293/#298). On Node 24 with a
+     * 660-test extraction suite this reproduced on every run at the same test.
+     * V8 flags are process-global, so the parse worker threads a test spawns
+     * are covered too.
+     */
+    poolOptions: { forks: { execArgv: [...WASM_RUNTIME_FLAGS] } },
     coverage: {
       provider: 'v8',
       reporter: ['text', 'json', 'html'],