refactor(voice): extract reusable Pocket primitives

Signed-off-by: John Tennant <johnmatthewtennant@gmail.com>

scripts/run-tests.sh

@@ -84,6 +84,9 @@ run_unit_tests() {
   run_test_step "buzz-auth unit tests" \
     cargo test -p buzz-auth --lib -- --nocapture
 
+  run_test_step "buzz-voice tests" \
+    cargo test -p buzz-voice --lib -- --nocapture
+
   # buzz-db migrator/lint unit tests (no infra): guard the embedded-migrator
   # invariant (exactly the consolidated 0001; cutover/backfill stays an operator
   # script, not startup state) and the tenant-scoping lints. The Postgres-backed