Find the new group by its hex id, not by a number

aGroupIsCreatedAndListed waited for a row matching `group-\d+`. The relay
mints group ids with randomHexToken(), so the tag is `group-` plus 64 hex
characters, and the pattern only matched when the id happened to start
with a digit: ten times in sixteen. The rest of the time the test failed
with "the group never appeared in the list after Create" while the dump
showed the group in the list ("Test Crew, peer96035270, You", tag
group-eea4ceeb...).

Now `group-[0-9a-f]{16,}`, which matches that tag and still not
`group-name` or `group-member-N`. Checked both patterns against the tag
from the failing run: old no match, new match. On device: passes.

The keyboard was ruled out first: with it fully open (top at y=1517) the
member row and Create sat at y=1201-1377, above it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/src/androidTest/kotlin/io/flamenet/messenger/app/FeatureUseTest.kt

@@ -130,8 +130,13 @@ class FeatureUseTest {
         compose.onNodeWithTag("create-group").performClick()
 
         // The group list carries a `group-<id>` row once the relay answers.
+        // The id is the relay's randomHexToken(), not a number. Matching
+        // `group-\d+` only worked when the hex happened to start with a digit,
+        // ten times in sixteen, so the test failed a third of the time on a
+        // group that was plainly there. Sixteen or more hex characters keeps
+        // `group-name` and `group-member-N` from matching instead.
         awaitNodeMatching(
-            Regex("group-\\d+"),
+            Regex("group-[0-9a-f]{16,}"),
             150_000,
             "the group never appeared in the list after Create",
         )