Arrival time fix perhaps (#11274)

* Add explicit presence for MeshPacket.rx_time (arrival time)

rx_time is now proto3 optional with a has_rx_time presence bit, matching
the rx_rssi treatment. A node with no GPS and no phone connected yet has
no time source at all, so a bare 0 was indistinguishable from a genuine
1970-01-01 reading; downstream consumers (replay packets, JSON
serialization) now check has_rx_time instead of the value.

* Dedupe rx_time stamping into a shared helper; trim a debug log string

Extract the repeated haveTime/rx_time/has_rx_time stamp logic (5 call
sites across Router.cpp, MeshBeaconModule.cpp, MeshService.cpp) into
Router::computeRxTimeStamp()/stampRxTime(). Also shorten the new RTC.cpp
LOG_DEBUG string. Saves 48 bytes of flash on rak4631 (measured), no
behavior change.

* Fix has_rx_rssi presence carried unconditionally through StoreForward replay

preparePayload() set has_rx_rssi = true unconditionally on replay, regardless
of whether the packet's rx_rssi at store time was a genuine measurement (e.g.
MQTT-relayed packets carry no real RSSI). Store the presence bit alongside
rx_rssi in PacketHistoryStruct and restore it on replay instead.

Flagged by Copilot on #11271 (same root cause the has_rx_time explicit
presence work fixes) but never addressed before that PR merged.

* Trim comment blocks to the repo's 1-2 line guideline

.github/copilot-instructions.md:338 caps code comments at 1-2 lines; several
blocks added across the rx_time explicit-presence work ran well past that.
Also consolidates Time.cpp's file-level doc comment into Time.h, where the
rest of the Time:: API contract already lives.

No behavior change.

* Add rx_time explicit-presence test coverage

- test_meshpacket_serializer: has_rx_time=false fixture plus tests asserting
  JsonSerialize/JsonSerializeEncrypted emit 0 rather than leaking the
  millis() placeholder, alongside the has_rx_time=true baseline.
- test_stream_api: two tests driving a real PhoneAPI handshake (want_config_id
  through STATE_SEND_PACKETS) that simulate a phone time-giving transaction
  arriving before vs. after a queued packet is drained - covering both the
  reconciled and the ships-with-placeholder-absent paths of
  MeshService::reconcilePendingRxTimes().

* Fix three correctness issues flagged in review

- Time.h: drop the reserved-identifier include guard (_MT_TIME_H); pragma
  once already covers it, matching convention elsewhere (e.g. RTC.h).
- Time.cpp: rebase getMillis64()'s wrap accumulator when the test seam
  swaps clock sources, so a real<->injected clock jump isn't miscounted
  as a genuine 32-bit wrap.
- NodeInfoModule: the 12h reply-suppression window is a local dedup
  duration, not a wall-clock reading - switch it to Time::getMillis64()
  so RTC-quality jumps and replayed packets' stale rx_time can't perturb
  it.
- StoreForwardModule: has_rx_time was derived from *current* RTC quality
  at replay time rather than stored at capture time, so a history entry
  saved while time-blind could be misreported as a valid epoch once the
  clock later improved. Persist the presence bit in PacketHistoryStruct
  instead.

* tryfix CI

* post review fixes

* more test fixes

src/gps/RTC.cpp

@@ -2,6 +2,7 @@
 #include "configuration.h"
 #include "detect/ScanI2C.h"
 #include "main.h"
+#include "mesh/MeshService.h"
 #include "modules/NodeInfoModule.h"
 #include <Throttle.h>
 #include <sys/time.h>
@@ -17,12 +18,16 @@ uint32_t lastSetFromPhoneNtpOrGps = 0;
 static uint32_t lastTimeValidationWarning = 0;
 static const uint32_t TIME_VALIDATION_WARNING_INTERVAL_MS = 15000; // 15 seconds
 
-static void triggerNodeInfoCheckOnTimeSource(RTCQuality oldQuality, RTCQuality newQuality)
+static void onTimeSourceQualityChanged(RTCQuality oldQuality, RTCQuality newQuality)
 {
     if (oldQuality == RTCQualityNone && newQuality > RTCQualityNone && nodeInfoModule) {
         LOG_DEBUG("Time source acquired (%s -> %s), triggering NodeInfo recheck", RtcName(oldQuality), RtcName(newQuality));
         nodeInfoModule->triggerImmediateNodeInfoCheck();
     }
+    if (oldQuality < RTCQualityFromNet && newQuality >= RTCQualityFromNet && service) {
+        LOG_DEBUG("RTC net quality reached (%s -> %s), reconciling rx_time", RtcName(oldQuality), RtcName(newQuality));
+        service->reconcilePendingRxTimes();
+    }
 }
 
 RTCQuality getRTCQuality()
@@ -128,7 +133,7 @@ RTCSetResult readFromRTC()
             timeStartMsec = now;
             zeroOffsetSecs = tv.tv_sec;
             currentQuality = RTCQualityDevice;
-            triggerNodeInfoCheckOnTimeSource(oldQuality, currentQuality);
+            onTimeSourceQualityChanged(oldQuality, currentQuality);
         }
         return RTCSetResultSuccess;
     } else {
@@ -174,7 +179,7 @@ RTCSetResult readFromRTC()
             timeStartMsec = now;
             zeroOffsetSecs = tv.tv_sec;
             currentQuality = RTCQualityDevice;
-            triggerNodeInfoCheckOnTimeSource(oldQuality, currentQuality);
+            onTimeSourceQualityChanged(oldQuality, currentQuality);
         }
         return RTCSetResultSuccess;
     } else {
@@ -210,7 +215,7 @@ RTCSetResult readFromRTC()
                 timeStartMsec = now;
                 zeroOffsetSecs = tv.tv_sec;
                 currentQuality = RTCQualityDevice;
-                triggerNodeInfoCheckOnTimeSource(oldQuality, currentQuality);
+                onTimeSourceQualityChanged(oldQuality, currentQuality);
             }
             return RTCSetResultSuccess;
         }
@@ -235,7 +240,7 @@ RTCSetResult readFromRTC()
             timeStartMsec = now;
             zeroOffsetSecs = tv.tv_sec;
             currentQuality = RTCQualityDevice;
-            triggerNodeInfoCheckOnTimeSource(oldQuality, currentQuality);
+            onTimeSourceQualityChanged(oldQuality, currentQuality);
         }
         return RTCSetResultSuccess;
     }
@@ -381,7 +386,7 @@ RTCSetResult perhapsSetRTC(RTCQuality q, const struct timeval *tv, bool forceUpd
 #endif
 
         readFromRTC();
-        triggerNodeInfoCheckOnTimeSource(oldQuality, currentQuality);
+        onTimeSourceQualityChanged(oldQuality, currentQuality);
         return RTCSetResultSuccess;
     } else {
         return RTCSetResultNotSet; // RTC was already set with a higher quality time