chore(8.0): collapse dead defensive guards + redundant polyfills

Follow-up to the browser/cloud/threading sweep — everything that was guarding
against unreachable runtimes is now dead.

cacheManager.ts: Environment enum + this.environment field removed (only NODE
was reachable). StorageType narrowed to MEMORY + FILESYSTEM. navigator.deviceMemory
and performance.memory paths in detectOptimalCacheSize + detectAvailableMemory
deleted; node:os is the sole source. environmentConfig keeps the index signature
for future per-runtime tuning but only the node slot is wired.

Dead 'typeof window === undefined' guards (the check is always true on 8.0):
paramValidation, structuredLogger, mutex, brainy.ts stats block, and
networkTransport ws-dynamic-import all collapsed. IntegrationLoader's inverse
guard ('!== undefined' returning 'browser') deleted. mutex's createMutex default
type simplified from "(typeof window === 'undefined' ? 'file' : 'memory')" to
plain 'file'.

Redundant TextEncoder/TextDecoder polyfills: Node 22+ ships both as globals.
src/utils/textEncoding.ts deleted (applyTensorFlowPatch was named for a defunct
dep and only re-assigned globals already present). setup.ts collapsed to an
empty stable import target. unified.ts loses its applyTensorFlowPatch re-export.

modelAutoConfig.getModelPath() loses the unreachable trailing fallback now
that isNode() is effectively the only branch the function ever takes.

jsonProcessing.ts left unchanged — its 'typeof document' checks are value-shape
guards on the parsed JSON, not environment detection.

src/utils/paramValidation.ts

@@ -13,21 +13,17 @@ import { findCallerLocation } from './callerLocation.js'
 // Dynamic import for Node.js os and fs modules
 let os: any = null
 let fs: any = null
-if (typeof window === 'undefined') {
-  try {
-    os = await import('node:os')
-    fs = await import('node:fs')
-  } catch (e) {
-    // OS/FS modules not available
-  }
+try {
+  os = await import('node:os')
+  fs = await import('node:fs')
+} catch (e) {
+  // OS/FS modules not available
 }
 
-// Browser-safe memory detection
 const getSystemMemory = (): number => {
   if (os) {
     return os.totalmem()
   }
-  // Browser fallback: assume 4GB
   return 4 * 1024 * 1024 * 1024
 }
 
@@ -35,7 +31,6 @@ const getAvailableMemory = (): number => {
   if (os) {
     return os.freemem()
   }
-  // Browser fallback: assume 2GB available
   return 2 * 1024 * 1024 * 1024
 }