✨ Draw the hit timer chart with Grafima

[LeoColman]

Moves the hit timer's "Why 10 seconds?" chart from GraphView to Grafima. This
was the last com.jjoe64 usage, so the dependency, its entry in the
graph-view bundle and its licensee exception all leave with it. MPAndroidChart
stays behind for the three Stats charts.

Before / after

GraphView	Grafima

Both at rest, so the hold markers sit at 0 seconds on each curve.

What changes visually:

• Hold markers are smaller. Dot radius is a property of the chart rather
  than of a series, so the markers cannot be size-15 against default curve dots
  any more. They are separated by colour instead, the same treatment the
  withdrawal charts already use.
• Y ticks land on 0/12/24/36/48/60 rather than 0/20/40/60, and x ticks on
  the three measured points rather than every 5 seconds. Grafima picks its own
  tick counts.
• Vertical gridlines are switched back on to match GraphView. Reading where ten
  seconds falls is the entire point of the chart.

Two things worth knowing for the next migration

Grafima animates, GraphView did not. The old chart lived in an AndroidView,
outside Compose's clock. Once the chart moved inside it, an animation that never
settles kept Compose busy, which stalled the timer's own recomposition:
ComposeHitTimerTest's "Start" and "Reset" both failed on a 20s timeout waiting
for the countdown to advance. There is no flag to disable animation, so the
specs are snap(). That is also the behaviour we want here, since the marker
tracks a running timer and a morph spec would always draw where the hold was.

The x axis labels come from each LineDataPoint's own label, not from
axisConfig's formatter. They were rendering as 10.0 because the label was
seconds.toString(). Setting xLabelFormatter looks like the fix and does
nothing at all.

Other

holdPointOn and the two study series drop GraphView's DataPoint for a
SubjectiveHighPoint with value equality, which lets WhyTenSecondsTest stop
comparing rendered strings.

Release APK 11,076,168 -> 11,049,255 bytes (-26,913, -0.24%), measured by
building both sides. Nice counterweight to the +32 KB Grafima cost in #1124.

Verification

• ./gradlew test detekt licensee green
• 25 instrumented tests green on the API 34 managed device
• assembleFdroidRelease green through R8; no com/jjoe64 entries left in the APK
• Driven by hand on an emulator: chart renders, and the markers track along both
  curves while a hold runs

---

The two screenshots live on the assets/hittimer-grafima branch so they stay
out of this diff and out of main. Delete that branch whenever this merges.

🤖 Generated with Claude Code

https://claude.ai/code/session_0167SJeKBmjmzhj9gNWcZYfs