refactor: runtime isolation — deprecate global singletons, add counter resets

config.ts: @deprecated on configure/getConfig/project/getProjectConfig.
  Current code has zero production callers — dead code path. Functions
  remain for backward compatibility but signal migration to scoped config.

context.ts: @deprecated on setDefaultContext. Documents that consumers
  should call resetDefaultContext() after use in tests to prevent
  context-seed leakage.

pipeline.ts: Export resetTraceCounter() for test isolation of _traceId
  counter variable.

extraction.ts: Export resetPageCacheNamespaceCounter() for test
  isolation of pageCacheNamespaceCounter.

Combined with prior fix (defaultPredicatesRegistered→sentinel check
+ compatibilityWarningEmitted→warnedUis WeakSet), 5 of 7 correctness-
  affecting global mutable state items are now tied down. Remaining:
  globalPredicateRegistry/globalClauseRegistry (already @deprecated
  with explicit injection path via LogicEngineOptions/EvalOptions).

605 SDK + 57 E2E = 662 tests pass.

packages/imhotep-playwright/src/extraction.ts

@@ -96,6 +96,11 @@ export function resetExtractionPathStats(): void {
 const pageCacheNamespace = new WeakMap<Page, string>()
 let pageCacheNamespaceCounter = 0
 
+/** Reset the page cache namespace counter (for test isolation). */
+export function resetPageCacheNamespaceCounter(): void {
+  pageCacheNamespaceCounter = 0
+}
+
 function getPageCacheNamespace(page: Page): string {
   const existing = pageCacheNamespace.get(page)
   if (existing) return existing