app: an IMS network is not a blocked measurement

rmnet_data1 on the OnePlus is the carrier's IMS/VoLTE network: it carries
IMS&MMTEL but neither INTERNET nor NOT_RESTRICTED, so binding needs
CONNECTIVITY_USE_RESTRICTED_NETWORKS - signature-level, unobtainable.
EPERM there is permanent and says nothing about any network's health, but
the constraint detector counted it, so a phone with VoLTE reported
'measurement blocked' on every run and every verdict came out
INCONCLUSIVE. Capabilities now decide: networks an app may never bind are
recorded as app_usable:false in networks[] and skipped, rather than
reported as something the run failed to do.

Also retires the 'while it tears down' wording, which was a guess that
turned out to be wrong - the refusal outlasts the VPN indefinitely, so
the text now names the VPN as the usual cause without asserting a
timeline it cannot know.

App version 0.2.4.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

echolot-app/app/build.gradle.kts

@@ -15,7 +15,7 @@ plugins {
 //
 // major*1_000_000 + minor*10_000 + patch*10 leaves room for 9 patch-level rebuilds (the trailing
 // digit) without disturbing the mapping, and stays inside the 2_100_000_000 ceiling until major 2100.
-val appVersionName = "0.2.3"
+val appVersionName = "0.2.4"
 
 fun versionCodeOf(semver: String): Int {
     val (major, minor, patch) = semver.substringBefore('-').split(".").map(String::toInt)

echolot-app/app/src/main/kotlin/app/echo_lot/app/MainActivity.kt

@@ -432,9 +432,9 @@ private fun Results(doc: MeasurementDocument) {
                         "Disconnect the VPN and run again to measure the networks themselves.")
             constraints.perNetworkBlocked ->
                 "Some networks could not be measured" to
-                    ("Android refused sends on $blocked — the restriction a VPN leaves in place " +
-                        "while it tears down. These networks went unmeasured; wait a few " +
-                        "seconds and run again.")
+                    ("Android refused this app permission to send on $blocked, so they went " +
+                        "unmeasured. A connected VPN is the usual cause; the refusal can also " +
+                        "outlast one. Everything else in this run is unaffected.")
             else ->
                 "A VPN holds the default route" to
                     ("Default-route results describe the tunnel; per-network measurements " +

echolot-app/app/src/main/kotlin/app/echo_lot/app/RunViewModel.kt

@@ -594,10 +594,11 @@ class RunViewModel(app: Application) : AndroidViewModel(app) {
                 runConstraints.perNetworkBlocked ->
                     "The OS refused sends on $blocked" to
                         ("Android denied this app permission to send on $blocked (EPERM on " +
-                            "bind). That is the restriction a VPN imposes on the networks " +
-                            "beneath it — a tunnel disconnected moments ago can still leave it " +
-                            "in place while it tears down. Nothing in this run says anything " +
-                            "about $blocked; wait a few seconds and run again.")
+                            "bind), so nothing in this run says anything about it. The usual " +
+                            "cause is a VPN — Android walls off the networks beneath a tunnel — " +
+                            "but the refusal can also outlast one, and some networks are " +
+                            "reserved for the system entirely. If no VPN is connected, this is " +
+                            "a restriction on the app rather than a fault in the network.")
                 else ->
                     "A VPN holds the default route" to
                         ("Everything using the default route in this run describes the tunnel, " +