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/classify-path-environment.test.ts

@@ -0,0 +1,56 @@
+import { describe, expect, it } from "bun:test"
+
+import {
+  classifyPathEnvironment,
+  describePathClassification,
+} from "./classify-path-environment"
+
+describe("classifyPathEnvironment", () => {
+  it("classifies macOS iCloud path as icloud", () => {
+    expect(
+      classifyPathEnvironment(
+        "/Users/x/Library/Mobile Documents/com~apple~CloudDocs/project/file.txt",
+      ),
+    ).toBe("icloud")
+  })
+
+  it("classifies OneDrive path on unix style", () => {
+    expect(classifyPathEnvironment("/Users/x/OneDrive/foo")).toBe("onedrive")
+  })
+
+  it("classifies OneDrive path on windows style", () => {
+    expect(classifyPathEnvironment("C:\\Users\\x\\OneDrive\\foo")).toBe("onedrive")
+  })
+
+  it("classifies macOS Desktop path as desktop-sync", () => {
+    expect(classifyPathEnvironment("/Users/x/Desktop/foo")).toBe("desktop-sync")
+  })
+
+  it("classifies /Volumes path as network-drive", () => {
+    expect(classifyPathEnvironment("/Volumes/NetworkShare/foo")).toBe("network-drive")
+  })
+
+  it("classifies random path as unknown", () => {
+    expect(classifyPathEnvironment("/tmp/foo")).toBe("unknown")
+  })
+
+  it("classifies empty string as unknown", () => {
+    expect(classifyPathEnvironment("")).toBe("unknown")
+  })
+
+  it("matches OneDrive case-insensitively", () => {
+    expect(classifyPathEnvironment("/Users/x/oNeDrIvE/foo")).toBe("onedrive")
+  })
+})
+
+describe("describePathClassification", () => {
+  it("returns human-readable descriptions", () => {
+    expect(describePathClassification("icloud")).toBe("iCloud Drive")
+    expect(describePathClassification("onedrive")).toBe("OneDrive")
+    expect(describePathClassification("desktop-sync")).toBe("Desktop sync (macOS)")
+    expect(describePathClassification("network-drive")).toBe("Network drive")
+    expect(describePathClassification("unknown")).toBe(
+      "filesystem that does not support fsync",
+    )
+  })
+})