test: replace fixed convergence timeouts with progress-aware connectivity wait

Add wait_until_connected to the shared convergence helpers: it polls a
suite's own pairwise pings (the signal it actually asserts on), returns
as soon as every pair is reachable, extends its deadline while the
reachable-pair count is still climbing, and gives up only when progress
stalls.

Use it in the rekey, static-mesh, and sidecar suites in place of the
fixed wall-clock baseline timeout and the blind sleep, which timed out
under concurrent CI load while the mesh was still converging.

testing/static/scripts/ping-test.sh

@@ -71,23 +71,6 @@ ping_all_quiet() {
     done
 }
 
-# Wait until all ping pairs succeed or timeout.
-wait_for_full_connectivity() {
-    local timeout="${1:-30}"
-    local start_secs=$SECONDS
-
-    while (( SECONDS - start_secs < timeout )); do
-        ping_all_quiet
-        if [ "$FAILED" -eq 0 ]; then
-            echo "  All $PASSED pairs reachable after $((SECONDS - start_secs))s"
-            return 0
-        fi
-        sleep 1
-    done
-    echo "  TIMEOUT: $PASSED passed, $FAILED failed after ${timeout}s"
-    return 1
-}
-
 echo "=== FIPS Ping Test ($PROFILE topology) ==="
 echo ""
 
@@ -108,8 +91,12 @@ elif [ "$PROFILE" = "mesh" ] || [ "$PROFILE" = "mesh-public" ]; then
     wait_for_peers fips-node-d 3 20 || true
     wait_for_peers fips-node-e 3 20 || true
 fi
-# Wait for FSP-level connectivity (discovery + session establishment)
-wait_for_full_connectivity 30 || true
+# Wait for full pairwise connectivity, progress-aware: the actual pings
+# are the convergence signal, the deadline extends while more pairs come
+# up, and it only gives up if progress stalls — so it does not
+# false-time-out under load while routing is still converging. The
+# directed-pair ping assertions below remain the actual test.
+wait_until_connected ping_all_quiet 45 15 || true
 
 # Reset counters for the actual test
 PASSED=0