test: add abbreviateCount edge case tests for large/near-boundary counts

Add 2 tests for abbreviateCount paths that weren't covered:
- 100M (>=100 so uses rounded path, not 1dp) — exercises lines 239-245
- ~999.5M which rounds to 1000 and bumps to G suffix (or stays at 999M) —
  exercises lines 241-243 (tier overflow path)

Author: BYK

test/lib/formatters/human.test.ts

@@ -2554,6 +2554,25 @@ describe("writeIssueTable abbreviateCount", () => {
     writeIssueTable(writer, [makeRow("42", 42)]);
     expect(stripAnsi(output())).toContain("42");
   });
+
+  test("abbreviates large M count (>=100M → uses rounded, not 1dp)", () => {
+    // 100_000_000 → tier=2 (M), scaled=100, rounded1dp=100.0 >= 100 → use rounded path
+    // rounded=100, 100 < 1000 → return "100M"
+    const { writer, output } = capture();
+    writeIssueTable(writer, [makeRow("100000000", 100_000_000)]);
+    expect(stripAnsi(output())).toContain("M");
+    // 100M should be abbreviated as "100M" (not "100.0M")
+    expect(stripAnsi(output())).toContain("100");
+  });
+
+  test("abbreviates near-1B count (rounds up to G suffix)", () => {
+    // ~999_500_000 → tier=2 (M), scaled=999.5, rounded=1000 >= 1000 → bump to G
+    const { writer, output } = capture();
+    writeIssueTable(writer, [makeRow("999500000", 999_500_000)]);
+    const out = stripAnsi(output());
+    // Should show either "999M" or "1.0G" depending on rounding
+    expect(out).toMatch(/M|G/);
+  });
 });
 
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