swarm-ui: keep the issue report's table, errors and repo filter consistent

A failed report dropped its error under the previous repo's rows, the
repo list and the report shared one error slot, a remembered repo that
the list lacked left the select on all repos, and the report URL did not
encode the repo path. Each request now has its own error, a failed report
clears the rows, the remembered repo keeps an option, and the path parts
are encoded.

frontend/packages/swarm-ui/test/issue-report-repo.test.mjs

@@ -0,0 +1,55 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import {
+  ALL_REPOS,
+  reportUrl,
+  repoOptions,
+} from "../src/pages/issue-report-repo.ts";
+
+test("reportUrl: no repo means the combined report", () => {
+  assert.equal(reportUrl(ALL_REPOS), "/api/issue-report");
+});
+
+test("reportUrl: a filter without a slash is not a repo", () => {
+  assert.equal(reportUrl("nope"), "/api/issue-report");
+});
+
+test("reportUrl: org and name become two path segments", () => {
+  assert.equal(
+    reportUrl("hyperhive/hyperhive"),
+    "/api/repos/hyperhive/hyperhive/issue-report",
+  );
+});
+
+test("reportUrl: reserved characters in a name are encoded", () => {
+  assert.equal(
+    reportUrl("org/a?b#c%d"),
+    "/api/repos/org/a%3Fb%23c%25d/issue-report",
+  );
+});
+
+test("repoOptions: all repos comes first, then the list", () => {
+  assert.deepEqual(repoOptions(["a/x", "b/y"], ALL_REPOS), [
+    { value: "", label: "all repos" },
+    { value: "a/x", label: "a/x" },
+    { value: "b/y", label: "b/y" },
+  ]);
+});
+
+test("repoOptions: a listed selection adds nothing", () => {
+  assert.equal(repoOptions(["a/x"], "a/x").length, 2);
+});
+
+test("repoOptions: a remembered repo keeps an option before the list loads", () => {
+  assert.deepEqual(repoOptions(null, "a/x"), [
+    { value: "", label: "all repos" },
+    { value: "a/x", label: "a/x" },
+  ]);
+});
+
+test("repoOptions: a remembered repo missing from the list says why", () => {
+  assert.deepEqual(repoOptions(["b/y"], "a/x").at(-1), {
+    value: "a/x",
+    label: "a/x (no open issues)",
+  });
+});