feat(sidebar): make listening ports clickable to open in browser (#1844)

* feat(sidebar): make listening ports clickable to open in browser

Wrap each sidebar port in a Button that opens http://localhost:{port}
in the cmux built-in browser (or system browser as fallback), matching
the existing PR link click behavior.

Fixes #1602

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

* fix: address bot review feedback on port clickability

- Localize port label text with String(localized:) instead of bare literal
- Add sidebar.port.label and sidebar.port.openTooltip keys to
  Localizable.xcstrings with English and Japanese translations
- Respect openSidebarPullRequestLinksInCmuxBrowser user preference in
  openPortLink, matching the openPullRequestLink pattern exactly

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

---------

Co-authored-by: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Resources/Localizable.xcstrings

@@ -64785,6 +64785,40 @@
         }
       }
     },
+    "sidebar.port.label": {
+      "extractionState": "manual",
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": ":%lld"
+          }
+        },
+        "ja": {
+          "stringUnit": {
+            "state": "translated",
+            "value": ":%lld"
+          }
+        }
+      }
+    },
+    "sidebar.port.openTooltip": {
+      "extractionState": "manual",
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Open localhost:%lld"
+          }
+        },
+        "ja": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "localhost:%lldを開く"
+          }
+        }
+      }
+    },
     "sidebar.pullRequest.openTooltip": {
       "extractionState": "manual",
       "localizations": {