feat(lanes): name the files behind a lane's uncommitted counts

GET /api/lanes/:id/git now returns `files`, the raw `git status --porcelain`
lines the dirty/untracked counts were already parsed from, capped at 20 so a
lane mid-`npm install` cannot ship thousands of paths through a polled
endpoint. The lane card hovers them as the tooltip on its
"N modified · N untracked" text, appending "… +N" when the cap bit.

No new subprocess and no new endpoint — statusCounts was counting those lines
and throwing them away.

client/src/components/lanes/LaneCard.tsx

@@ -539,7 +539,20 @@ export default function LaneCard({
             <span className="shrink-0 text-fg-muted">{git.head}</span>
             <span className="truncate text-fg-muted">{git.subject}</span>
             {(git.dirty > 0 || git.untracked > 0) && (
-              <span className="shrink-0 text-status-warning/80">
+              <span
+                className="shrink-0 cursor-help text-status-warning/80"
+                /* Native title: the counts' own file list, capped server-side.
+                   A hover card would need a portal to escape this truncating
+                   row — the browser's tooltip already escapes it for free. */
+                title={
+                  git.files?.length
+                    ? git.files.join("\n") +
+                      (git.dirty + git.untracked > git.files.length
+                        ? `\n… +${git.dirty + git.untracked - git.files.length}`
+                        : "")
+                    : undefined
+                }
+              >
                 {t("git.uncommitted", { dirty: git.dirty, untracked: git.untracked })}
               </span>
             )}

client/src/components/lanes/__tests__/LaneCard.test.tsx

@@ -207,6 +207,7 @@ describe("LaneCard git block", () => {
     subject: "free-text rule mode in the form",
     dirty: 2,
     untracked: 1,
+    files: [" M server/lib/alerts.js", " M client/src/lib/api.ts", "?? scratch.txt"],
   };
 
   it("renders the live branch, head, subject and uncommitted counts", async () => {
@@ -218,6 +219,10 @@ describe("LaneCard git block", () => {
     expect(block.textContent).toContain("9b3e74a");
     expect(block.textContent).toContain("free-text rule mode in the form");
     expect(block.textContent).toContain("2");
+    // Hovering the counts names the files behind them.
+    expect(screen.getByText(/modified/).title).toBe(
+      " M server/lib/alerts.js\n M client/src/lib/api.ts\n?? scratch.txt"
+    );
     // The live branch replaces the lane's recorded one rather than doubling it.
     expect(screen.queryByText(/stale\/recorded/)).toBeNull();
   });