feat(shared): add fsync-skip tracker and path-environment classifier

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/shared/fsync-skip-tracker.ts

@@ -0,0 +1,42 @@
+import type { PathClassification } from "./classify-path-environment"
+
+export type FsyncSkipEntry = {
+  filePath: string
+  contextLabel: string
+  errorCode: string
+  message: string
+  pathClassification: PathClassification
+  timestamp: number
+}
+
+const MAX_SKIPS = 200
+const fsyncSkips: FsyncSkipEntry[] = []
+
+export function recordFsyncSkip(entry: Omit<FsyncSkipEntry, "timestamp">): void {
+  fsyncSkips.push({ ...entry, timestamp: Date.now() })
+
+  if (fsyncSkips.length > MAX_SKIPS) {
+    fsyncSkips.splice(0, fsyncSkips.length - MAX_SKIPS)
+  }
+}
+
+export function drainSkipsAfter(timestampMs: number): FsyncSkipEntry[] {
+  const drainedEntries: FsyncSkipEntry[] = []
+  const retainedEntries: FsyncSkipEntry[] = []
+
+  for (const entry of fsyncSkips) {
+    if (entry.timestamp > timestampMs) {
+      drainedEntries.push(entry)
+      continue
+    }
+
+    retainedEntries.push(entry)
+  }
+
+  fsyncSkips.splice(0, fsyncSkips.length, ...retainedEntries)
+  return drainedEntries
+}
+
+export function clearAllSkips(): void {
+  fsyncSkips.length = 0
+}