HKL3D viewer layout: connect toggle, dock column, remembered layout

[pecomyint]

Stacked on #189 — review/merge that one first; this diff shows only this PR's change.

Summary

• One Connect/Disconnect toggle; compact connection row that no longer crops the channel field.
• Docks in one scrollable right-hand column (Plot Mode, Live Grid, Stats/Image tabs).
• Window geometry and dock layout persist via QSettings (_DOCK_STATE_VERSION).
• Reset Camera is connected (isometric view + fit) with a tooltip.

Test plan

• pytest tests/unit passes; ruff check src/dashpva/ clean
• New tests in test_hkl_viewer_layout.py
• Open at default size: nothing cropped; resize/close/reopen restores layout

🤖 Generated with Claude Code

[pecomyint]

#172 is the general BaseWindow persistence foundation and should land first for issue #85. When this stacked PR is eventually rebased after #172/#189, please remove or adapt the HKL3D-specific QSettings geometry/dock implementation so there is one persistence owner. Keep this PR's targeted layout, connect-toggle, dock-column, and reset-camera improvements; only the duplicated persistence path needs reconciliation.