feat(ui): E31 S4a — rail rows are links, the channel page opens on unwatched, users and audit tidied

- Nav rail page rows are real links (/?page=<id>): a middle-click or
  Ctrl-click opens the page in a new tab; a plain click stays in-app.
- A fresh channel page shows the unwatched videos; a picked watch state
  is a remembered preference (channelShow).
- Users: the role, suspend and delete move into the row's one menu
  (the "…", right-click, Shift+F10); locked ones keep their reason.
- Audit log: back-to-back successful runs of one job fold into one row
  that opens to the earlier ones; a failed run reads in the danger colour.
- DESIGN.md decision log: the E31 picks.

frontend/src/lib/auditGroups.test.ts

@@ -0,0 +1,60 @@
+// E31: the audit log's first screen was one job's "done" ten times over. Back-to-back successful runs
+// of one job fold into one row; a failure, a skip, another job or an admin's own action breaks the run.
+import { describe, expect, it } from "vitest";
+import type { AuditRow } from "./api";
+import { foldJobRuns } from "./auditGroups";
+
+let nextId = 1;
+const run = (job: string, status = "ok"): AuditRow => ({
+  id: nextId++,
+  created_at: null,
+  actor: null,
+  action: "job_run",
+  target_type: "job",
+  target_id: job,
+  summary: null,
+  before: null,
+  after: { status },
+});
+const admin = (): AuditRow => ({ ...run("x"), action: "config_set", target_type: "config" });
+
+const shape = (rows: ReturnType<typeof foldJobRuns>) =>
+  rows.map((r) => `${r.target_id}:${String(r.after?.status)}×${r.runs?.length ?? 1}`);
+
+describe("folding the job runs", () => {
+  it("folds back-to-back successful runs of one job, newest first", () => {
+    const rows = [run("enrich"), run("enrich"), run("enrich"), run("people")];
+    const out = foldJobRuns(rows);
+    expect(shape(out)).toEqual(["enrich:ok×3", "people:ok×1"]);
+    expect(out[0]!.id).toBe(rows[0]!.id);
+    expect(out[0]!.runs!.map((r) => r.id)).toEqual(rows.slice(0, 3).map((r) => r.id));
+  });
+
+  it("never folds a failed or skipped run, and lets it break the run", () => {
+    const rows = [run("rss"), run("rss", "error"), run("rss", "error"), run("rss"), run("rss")];
+    expect(shape(foldJobRuns(rows))).toEqual([
+      "rss:ok×1",
+      "rss:error×1",
+      "rss:error×1",
+      "rss:ok×2",
+    ]);
+    expect(shape(foldJobRuns([run("rss", "skipped"), run("rss", "skipped")]))).toEqual([
+      "rss:skipped×1",
+      "rss:skipped×1",
+    ]);
+  });
+
+  it("keeps an admin's own action between two runs, and the runs apart", () => {
+    expect(shape(foldJobRuns([run("enrich"), admin(), run("enrich")]))).toEqual([
+      "enrich:ok×1",
+      "x:ok×1",
+      "enrich:ok×1",
+    ]);
+  });
+
+  it("leaves the rows it was given as they were", () => {
+    const rows = [run("enrich"), run("enrich")];
+    foldJobRuns(rows);
+    expect("runs" in rows[0]!).toBe(false);
+  });
+});