Add PM5 regression tests from issue #3686 debug log

Validates that PR #4610's PM5-without-FTMS parsing fix does not regress
other real-world Concept2 PM5 tickets. Adds two tests exercising the shared
production parser (ftmsrower::processPm5ParserState) with actual packets
extracted from the #3686 debug log ("Metrics at 0 with Concept 2 PM5
Rowerg"):

- Pm5WithoutFtmsSustainedIdleBurstFromIssue3686MustNotDriftDistance: the
  device repeated the same idle CE060031/CE060032 payload (RowState == 0)
  for ~21s after connecting; distance must stay pinned and speed/cadence
  must stay at 0 the whole time.
- Pm5WithoutFtmsActiveTransitionFromIssue3686MustAdvanceMetrics: once
  RowState flips from 0 to 1, distance must resume advancing and
  speed/cadence must become positive again.

Surveyed other Concept2/PM5-tagged tickets (#4244, #3503, #1856, #1486) but
none of them exercise this code path: #4244 and part of #1486 use the CSAFE
serial protocol (csaferower.cpp), #3503's PM5 is handled by ftmsbike.cpp,
and the rest of #1856/#1486 never reach a successful device connection in
the logs. Full test suite (552 tests) still passes with 0 failures.

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

Author: cagnulein

tst/Devices/TestFtmsRowerPm5Regression.h

@@ -50,6 +50,33 @@ class FtmsRowerPm5RegressionTest : public testing::Test {
     static PacketSample concept2ZeroDistancePacket32FromIssue3872Log() {
         return {1763131313972LL, fromHex("000000000000ff00000000000000000000")};
     }
+
+    // Extracted from debug-Sun_Sep_14_19_26_19_2025.log (#3686, "Metrics at 0 with
+    // Concept 2 PM5 Rowerg"). This PM5 has no FTMS service and reported the exact same
+    // CE060031/CE060032 payload (RowState idle, byte9 == 0) for roughly 48 seconds after
+    // connecting, which is what the reporter saw as "metrics stuck at 0". Distance must stay
+    // pinned at the value derived from that first packet the whole time, and speed/cadence must
+    // stay at 0 while idle.
+    static std::vector<PacketSample> concept2NoFtmsIdleBurstFromIssue3686Log() {
+        return {
+            {1757870782324LL, fromHex("2e0d00df0100010101000100000000000080e3")}, // 0031, RowState=0
+            {1757870782391LL, fromHex("2e0d008c034eff21d7177e0000000000")},       // 0032
+            {1757870796894LL, fromHex("2e0d00df0100010101000100000000000080e3")}, // 0031, RowState=0
+            {1757870796897LL, fromHex("2e0d008c034eff21d7177e0000000000")},       // 0032
+            {1757870803083LL, fromHex("2e0d00df0100010101000100000000000080e3")}, // 0031, RowState=0
+            {1757870803086LL, fromHex("2e0d008c034eff21d7177e0000000000")},       // 0032
+        };
+    }
+
+    // Extracted from the same #3686 log a few packets after the idle burst above, once the
+    // rower actually starts moving: RowState (byte9 of CE060031) flips from 0 to 1 and the
+    // reported distance advances from 0x0001df (479 dm) to 0x0001e1 (481 dm).
+    static std::vector<PacketSample> concept2NoFtmsActiveTransitionFromIssue3686Log() {
+        return {
+            {1757870830394LL, fromHex("4e0d00e10100010101010200000000000080e3")}, // 0031, RowState=1
+            {1757870830402LL, fromHex("4e0d004603a5ff2ae9a9890000000000")},      // 0032
+        };
+    }
 };
 
 TEST_F(FtmsRowerPm5RegressionTest, Pm5WithoutFtmsRealLogMustProducePositiveDistance) {
@@ -137,6 +164,81 @@ TEST_F(FtmsRowerPm5RegressionTest, Pm5WithFtmsMustIgnoreConcept2DistancePackets)
     EXPECT_TRUE(std::isfinite(state.distanceKm));
 }
 
+TEST_F(FtmsRowerPm5RegressionTest, Pm5WithoutFtmsSustainedIdleBurstFromIssue3686MustNotDriftDistance) {
+    // Regression for #3686 "Metrics at 0 with Concept 2 PM5 Rowerg": this real device sent the
+    // exact same idle CE060031/CE060032 payload repeatedly for ~21 seconds after connecting
+    // (RowState byte == 0 the whole time). Distance must stay pinned to the value derived from
+    // the very first packet, and speed/cadence must stay at 0, for as long as the device reports
+    // RowState == 0 - it must not drift up or down just because time passes.
+    ftmsrower::ParserRegressionState state;
+    state.hasFtmsService = false;
+
+    const auto idleBurst = concept2NoFtmsIdleBurstFromIssue3686Log();
+    ASSERT_EQ(idleBurst.size(), 6u);
+
+    // Intentionally exercise the shared production parser helper instead of re-implementing parsing here.
+    ftmsrower::processPm5ParserState(state, QStringLiteral("{ce060031-43e5-11e4-916c-0800200c9a66}"),
+                                     idleBurst[0].payload, idleBurst[0].timestampMs);
+    ftmsrower::processPm5ParserState(state, QStringLiteral("{ce060032-43e5-11e4-916c-0800200c9a66}"),
+                                     idleBurst[1].payload, idleBurst[1].timestampMs);
+    const double firstDistanceKm = state.distanceKm;
+    ASSERT_TRUE(state.rowStateReceived);
+    ASSERT_EQ(state.rowState, 0);
+    ASSERT_GT(firstDistanceKm, 0.0);
+    EXPECT_DOUBLE_EQ(state.speedKmh, 0.0);
+    EXPECT_DOUBLE_EQ(state.cadence, 0.0);
+
+    for (size_t i = 2; i < idleBurst.size(); i += 2) {
+        ftmsrower::processPm5ParserState(state, QStringLiteral("{ce060031-43e5-11e4-916c-0800200c9a66}"),
+                                         idleBurst[i].payload, idleBurst[i].timestampMs);
+        ftmsrower::processPm5ParserState(state, QStringLiteral("{ce060032-43e5-11e4-916c-0800200c9a66}"),
+                                         idleBurst[i + 1].payload, idleBurst[i + 1].timestampMs);
+        EXPECT_EQ(state.rowState, 0);
+        EXPECT_DOUBLE_EQ(state.speedKmh, 0.0);
+        EXPECT_DOUBLE_EQ(state.cadence, 0.0);
+        EXPECT_DOUBLE_EQ(state.distanceKm, firstDistanceKm)
+            << "distance must not drift while the PM5 keeps reporting RowState == 0";
+    }
+
+    EXPECT_TRUE(std::isfinite(state.distanceKm));
+}
+
+TEST_F(FtmsRowerPm5RegressionTest, Pm5WithoutFtmsActiveTransitionFromIssue3686MustAdvanceMetrics) {
+    // Regression for #3686: once the same real PM5 device actually starts rowing (RowState flips
+    // from 0 to 1), distance must advance past the idle-pinned value and speed/cadence must
+    // become non-zero. This is the exact recovery the reporter expected but initially did not see.
+    ftmsrower::ParserRegressionState state;
+    state.hasFtmsService = false;
+
+    const auto idleBurst = concept2NoFtmsIdleBurstFromIssue3686Log();
+    ASSERT_GE(idleBurst.size(), 2u);
+    ftmsrower::processPm5ParserState(state, QStringLiteral("{ce060031-43e5-11e4-916c-0800200c9a66}"),
+                                     idleBurst[0].payload, idleBurst[0].timestampMs);
+    ftmsrower::processPm5ParserState(state, QStringLiteral("{ce060032-43e5-11e4-916c-0800200c9a66}"),
+                                     idleBurst[1].payload, idleBurst[1].timestampMs);
+    const double idleDistanceKm = state.distanceKm;
+    ASSERT_EQ(state.rowState, 0);
+
+    const auto activeTransition = concept2NoFtmsActiveTransitionFromIssue3686Log();
+    ASSERT_EQ(activeTransition.size(), 2u);
+
+    // Intentionally exercise the shared production parser helper instead of re-implementing parsing here.
+    ftmsrower::processPm5ParserState(state, QStringLiteral("{ce060031-43e5-11e4-916c-0800200c9a66}"),
+                                     activeTransition[0].payload, activeTransition[0].timestampMs);
+    EXPECT_TRUE(state.rowStateReceived);
+    EXPECT_EQ(state.rowState, 1);
+    EXPECT_GE(state.distanceKm, idleDistanceKm);
+
+    ftmsrower::processPm5ParserState(state, QStringLiteral("{ce060032-43e5-11e4-916c-0800200c9a66}"),
+                                     activeTransition[1].payload, activeTransition[1].timestampMs);
+    EXPECT_GT(state.distanceKm, idleDistanceKm)
+        << "distance must advance once RowState leaves idle instead of staying stuck like the "
+           "reporter observed";
+    EXPECT_GT(state.speedKmh, 0.0);
+    EXPECT_GT(state.cadence, 0.0);
+    EXPECT_TRUE(std::isfinite(state.distanceKm));
+}
+
 TEST_F(FtmsRowerPm5RegressionTest, Pm5WithFtmsMustIgnoreConcept2DistanceEvenWhenConcept2DistanceIsPositive) {
     ftmsrower::ParserRegressionState state;
     state.hasFtmsService = true;