perf(executors): lazy-load the executor registry — defer class imports + construction to first use (#11220) (#11421)

Validated in a combined 3-PR batch worktree off release/v3.8.51 tip (a sibling PR from the same author, #11495, was held out — a typecheck error in zai-web.ts only reproduced with this PR + #11495 boarded together, and cleared without #11495; isolated this PR alone confirmed clean on its own too, so the interaction belonged to #11495's side — see its comment).
- Golden lock: executor-map-golden.test.ts — passes byte-identical (same keys, classes, provider identities, dispatch guards)
- Focused tests part of batch's 94/94 node:test run
- typecheck:core, file-size, changelog-integrity, complexity, cognitive-complexity — all OK
- Full-repo lint: 228 pre-existing dashboard react-hooks/* findings, unrelated to this diff

Thanks for the measured, careful methodology here — the golden-lock contract plus the isolated DATA_DIR benchmarking make this an easy PR to trust despite the wide surface (72 files).

scripts/check/check-known-symbols.ts

@@ -142,8 +142,8 @@ export function diffComboStrategies(
  * getExecutor() na função main().
  */
 export function extractExecutorAliases(indexSource: string): string[] {
-  const start = indexSource.indexOf("const executors = {");
-  if (start < 0) throw new Error("could not find `const executors = {` in executors/index.ts");
+  const start = indexSource.indexOf("const lazyExecutors");
+  if (start < 0) throw new Error("could not find 'const lazyExecutors' in executors/index.ts");
   const end = indexSource.indexOf("\n};", start);
   if (end < 0) throw new Error("could not find end of executors map (`\\n};`)");
   const block = indexSource.slice(start, end);