Add "Adapt to my typing" (adaptive key zones) – slim version from #676

[4di-hello]

As discussed in #676, this is the slimmer version of #671 for the 4.3.0 beta.

What it does

One switch in Text correction, off by default: "Adapt to my typing".

When on, the keyboard learns where the user touches each letter key, using the words that are finally committed as ground truth (autocorrected word, picked suggestion, reverted autocorrection, or a letter retyped after deleting a neighboring one). Once a key has 30 touches, a touch near the border to a neighboring key is assigned to the key the user most likely meant. The dictionary gets the corrected coordinates too, so autocorrection benefits as well. The shift is capped to a third of a key.

Your concerns from #671

• One switch, fixed strength: no strength slider, no separate "collect data" switch.
• Off = unchanged: with the switch off, nothing is recorded, nothing is loaded, and key detection runs the existing code path.
• Determinism: same data, same key. It only differs from today near key borders and only after enough data.
• Latency: per touch a few arithmetic operations on cached offsets, no I/O on the touch path.
• Footprint in core: ~68 changed lines, only single hook calls:
  • KeyDetector (+3/-1), PointerTracker (+5/-1), InputLogic (+9)
  • settings key/default/value (+4), navigation entry (+6), Text correction screen (+10/-1)
  • backup category for the typing profile in BackupRestorePreference (+25/-3)
• Everything else is in its own package latin/heatmap (TypingAdaptation, TypingHeatmap, KeyboardGeometry), plus the statistics screen and 17 unit tests.

Privacy

• Never active in password fields or incognito mode, no gestures.
• Stored only locally in no-backup storage (not in Android backups or device transfer). It only leaves the device in the keyboard's own backup, as a separate category.
• Touches are stored per key without order, so text can't be reconstructed.

Statistics screen

Text correction → "Typing heatmap": heatmap per key, most frequent misses, misses per week and misses before/after adaptation. Easy to drop if you prefer.

Tests

• TypingHeatmapTest: 17 tests, all pass.
• InputLogicTest: only the 8 caps* failures (Robolectric DYNAMIC_RECEIVER_NOT_EXPORTED_PERMISSION), which also fail on current main.
• In daily use on my device for several days (the earlier version from Add optional typing heatmap with adaptive key zones #671, same logic).

Closes #676