fix(clip): a clip is held to its owner's storage cap, and its limits and failures say the server's truth

- The cut file is measured against what its owner has left, for a YouTube range (whose fetch never
  reads yt-dlp's size ceiling) and for a Plex clip (which fetches nothing), before the fetch and
  again before it is placed; a refusal leaves the asset pending for a Retry.
- A silent Plex file is cut silent; a file the probe cannot read says so.
- A second job on a failed or renamed clip gets the same YouTube diagnosis and the fetched title.
- The "too long" refusal names the server's cap; a contract test holds the client's copies of the
  clip limits to clip.py; the shipped player clients are pinned against the installed yt-dlp.
- One HDR transfer set and one rating_key lookup; job status words from JobStatus; the display-name
  guard sees subscript writes and the clip route; stale comments and types follow the clip job.

frontend/src/lib/clipLimits.contract.test.ts

@@ -0,0 +1,35 @@
+import { readFileSync } from "node:fs";
+import { describe, expect, it } from "vitest";
+
+// The limits a clip is marked to, held in two languages: the clip panel's handles, fields and keys
+// keep a range the server takes, and a crop frame no smaller than it cuts. Neither side can see the
+// other's copy, so the gate reads both (as `api/downloads.contract.test.ts` does for the name bound).
+// A cap moved on one side alone makes the panel offer what the server refuses — or clamp below
+// what it would take — with every other test green.
+//
+// Read as TEXT: the modules are plain constants, but reading the source is what makes a renamed or
+// moved constant fail here instead of comparing two undefineds.
+const src = (u: string) => readFileSync(new URL(u, import.meta.url), "utf-8");
+const backend = src("../../../backend/app/downloads/clip.py");
+
+function pyConst(name: string): number {
+  const m = backend.match(new RegExp(`^${name}\\s*=\\s*([\\d.]+)`, "m"));
+  expect(m, `backend/app/downloads/clip.py no longer defines ${name}`).toBeTruthy();
+  return Number(m![1]);
+}
+
+function tsConst(file: string, name: string): number {
+  const m = src(file).match(new RegExp(`^(?:export )?const ${name} = ([\\d.]+);`, "m"));
+  expect(m, `${file} no longer defines ${name}`).toBeTruthy();
+  return Number(m![1]);
+}
+
+describe("clip limits", () => {
+  it.each([
+    ["./clipRange.ts", "MIN_CLIP_S"],
+    ["./clipRange.ts", "MAX_CLIP_S"],
+    ["./cropGeometry.ts", "MIN_CROP"],
+  ])("%s %s is the server's", (file, name) => {
+    expect(tsConst(file, name)).toBe(pyConst(name));
+  });
+});