test: tighten progressive-update assertions to count markers

The all-pending and partial state checks used substring presence,
which would also accept states with one pending plus one failed
or skipped row. The current setup only ever produces successes
and pendings so the looser checks happened to be equivalent in
practice — but readers couldn't tell that without inspecting
which statuses the orchestrator can emit.

Count hourglass and checkmark markers explicitly: the all-pending
state has exactly two hourglasses and zero checkmarks, the partial
state has exactly one of each. The contract is now visible at the
assertion site without requiring the reader to reason about which
other statuses might appear.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: korthout

src/test/backport.integration.test.ts

@@ -715,19 +715,22 @@ describe("Backport.run() orchestration", () => {
       const backport = new Backport(github, config, git);
       await backport.run();
 
-      // Find the targets-known update (all pending, no completed rows)
+      const countMatches = (body: string, marker: string) =>
+        (body.match(new RegExp(marker, "g")) ?? []).length;
+
+      // Targets-known update: both rows pending, no completed rows
       const allPending = github.updatedComments.find(
         (u) =>
-          u.body.includes(":hourglass:") &&
+          countMatches(u.body, ":hourglass:") === 2 &&
           !u.body.includes(":white_check_mark:"),
       );
       expect(allPending).toBeDefined();
 
-      // Find partial update (one completed, one pending)
+      // Partial update: exactly one completed, exactly one pending
       const partial = github.updatedComments.find(
         (u) =>
-          u.body.includes(":white_check_mark:") &&
-          u.body.includes(":hourglass:"),
+          countMatches(u.body, ":white_check_mark:") === 1 &&
+          countMatches(u.body, ":hourglass:") === 1,
       );
       expect(partial).toBeDefined();