feat(workout-ui): tabs with swipe for lap/chart, taller scan list, km chart markers

[Copilot]

The running-session card jumps when switching lap/graph views because the two views differ in height, the Bluetooth scan list is capped at ~6 devices despite free screen space, and the live chart gives no distance cues.

Stable lap/chart switching via tabs + swipe

• Replaced the MaterialButtonToggleGroup below the cards with a Material TabLayout above the card (portrait + landscape) — no new dependency.
• Wrapped lapSection and chartSection in a FrameLayout; the inactive card is now INVISIBLE instead of GONE, so the container always measures to the tallest view and the rectangle keeps a constant top/height.
• Added a horizontal fling detector to switch views (swipe left → chart, right → lap). Distance + velocity thresholds keep the chart's slow tooltip drag working.

Bluetooth scan list uses available space

• ScrollView now uses fillViewport; rvScanResults switched from fixed height (220dp / 160dp landscape) to layout_weight="1", keeping the old height as minHeight. The list grows to fill remaining space while the Start button stays at the bottom.

Kilometre markers in live chart

• MainActivity records the chart point index each time a full km is completed (persisted across rotation like the other live-chart state).
• LineChartView draws a labelled vertical line per marker:

val kmCount = sample.totalDistanceM / 1000
while (liveKmMarkIndices.size < kmCount) liveKmMarkIndices.add(liveSpeedPoints.size - 1)
// ...
binding.liveChart.setData(*seriesList.toTypedArray(), durationSec = durationSec,
    kmMarkIndices = liveKmMarkIndices.toList())

Also updated changelog 6.txt. Note: btnViewLap/btnViewChart ids changed type (MaterialButton → TabItem) consistently in both layout configurations for view binding.

[github-actions]

✅ Debug APK artifact is ready for commit d0416f4 .
💾 Download APK artifact here.
Workflow run: https://github.com/duhow/ftms-bridge/actions/runs/30207211748