fix(artifacts L6): keep the exact pinned file name (Codex r4 QjVD)

Pin path resolution no longer trims the path: `.env ` and `.env` are different files, and trimming pinned and showed the sibling. A blank path is still refused.

---

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<!-- mux-attribution: model=anthropic:claude-opus-5-5 thinking=high costs=158.12 -->

Author: ThomasK33

src/node/services/pinnedArtifactFiles.test.ts

@@ -156,6 +156,23 @@ describe("pinned workspace files", () => {
     ).toEqual({ success: true, data: { path: "README.md" } });
   });
 
+  test("pins the exact file name, edge whitespace included", async () => {
+    await fs.writeFile(path.join(checkout, ".env"), "plain");
+    await fs.writeFile(path.join(checkout, ".env "), "trailing space");
+    expect(await pinFile(context, { workspaceId: "ws", path: ".env " })).toEqual({
+      success: true,
+      data: { path: ".env " },
+    });
+    expect(await readPinnedFile(context, { workspaceId: "ws", path: ".env " })).toMatchObject({
+      success: true,
+      data: { status: "ok", content: "trailing space" },
+    });
+    // A blank path is still refused.
+    expect(await pinFile(context, { workspaceId: "ws", path: "  " })).toMatchObject({
+      success: false,
+    });
+  });
+
   test("multi-project workspaces have no pinned files", async () => {
     projects = [
       { projectPath: "/a", projectName: "a" },

src/node/services/pinnedArtifactFiles.ts

@@ -84,7 +84,9 @@ export function resolveCheckoutLocation(
  * checkout-relative POSIX path, or an error string.
  */
 export function toPinnedRelativePath(root: string, inputPath: string): string | { error: string } {
-  const trimmed = inputPath.trim();
+  // The exact bytes: `.env ` and `.env` are different files (Review keeps edge whitespace).
+  if (inputPath.trim().length === 0) return { error: "No file path given" };
+  const trimmed = inputPath;
   const normalizedRoot = root.replace(/[\\/]+$/, "");
   let relPath = trimmed.replace(/\\/g, "/");
   if (path.isAbsolute(trimmed) || trimmed.startsWith("/")) {
@@ -218,7 +220,8 @@ function resolvePinInput(
   inputPath: string,
   relativeTo: "tool-cwd" | "checkout" | null | undefined
 ): string {
-  const trimmed = inputPath.trim();
+  // Not trimmed: edge whitespace is part of the file name (see toPinnedRelativePath).
+  const trimmed = inputPath;
   if (relativeTo !== "tool-cwd" || path.isAbsolute(trimmed) || trimmed.startsWith("/")) {
     return trimmed;
   }