feat: add task count badges to interrupted, ready, and running tabs

- Add computeTabBadgeCounts(tasks) exported pure function
- Add updateTabBadges(tasks) that updates badge spans in tab buttons
- Call updateTabBadges on every poll regardless of active tab
- Add .tab-count-badge spans to interrupted/ready/running tab buttons in HTML
- Add CSS for .tab-count-badge pill styling (hidden when count is zero)
- Add 11 tests in web/test/tab-badges.test.mjs covering all states

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/web/style.css b/web/style.css
index ee1b69c..31f929e 100644
--- a/web/style.css
+++ b/web/style.css
@@ -111,6 +111,25 @@ header h1 {
   border-bottom-color: var(--accent);
 }
 
+.tab-count-badge {
+  display: inline-block;
+  margin-left: 0.3em;
+  padding: 0 0.4em;
+  border-radius: 999px;
+  font-size: 0.7em;
+  font-weight: 700;
+  line-height: 1.5;
+  background: var(--accent);
+  color: #fff;
+  vertical-align: middle;
+  min-width: 1.4em;
+  text-align: center;
+}
+
+.tab-count-badge[hidden] {
+  display: none;
+}
+
 /* Main layout */
 main {
   max-width: 640px;