camp#142: interactive colorbar dialog from the layer context menu (PR2 — closes #142)

[rolker]

Summary

PR2 of 2 for #142 — the interactive colorbar, completing the
operator-overridable colormap range. Replaces PR1's two sequential
QInputDialog prompts with a "Colormap range…" dialog opened from each scalar
layer's context menu (ADR-0009).

Closes #142.

What it does

• New raster/colormap_range_dialog.{h,cpp}
  (camp::raster::showColormapRangeDialog) — a modal dialog hosting
  marine_colormap_widgets::ColormapLegendWidget (drag the min/max handles) plus
  min/max spin boxes for precise entry, kept in sync with the bar. Edits fire
  live so the map re-renders while the dialog is open.
• Wired into GggsTileLayer, RasterLayer, and SonarLiveCacheLayer — one
  shared helper, so the three menus stay DRY (the duplicated numeric-prompt
  lambdas from PR1 are gone).
• Seeds the bar from a ColormapRangeState snapshot (palette index, data extents
  as the colorbar domain, current mode/lo/hi). An existing Manual override is
  displayed via ColormapLegendWidget::setManual — the slot added in
  marine_colormap#10 specifically so a consumer can open on a persisted override.
• rangeChanged fires for both a manual pin and an auto fold; the dialog
  disambiguates on mode() → setRangeOverride vs resetRangeToAuto.
• Build wiring: find_package(marine_colormap_widgets) + <depend> +
  link PRIVATE to camp_map (used only in the .cpp; the public header
  forward-declares QWidget).

Design

ADR-0009 records the placement decision (modal context-menu dialog vs docked
panel vs map overlay) and the seed/dispatch contract.

Testing

Host build clean; 151 tests, 0 errors, 0 failures, 1 skipped (container can't
build camp's lower-layer deps; host-verified).

The dialog is thin Qt glue over already-tested components — the widget's
setManual/drag/reset/rangeChanged (marine_colormap gtest) and the layers'
setRangeOverride/resetRangeToAuto/persistence (PR1 test_range_persist). The
modal exec() event loop makes the glue itself impractical to unit-test
headlessly, so it's validated by manual exercise (as the #108 band picker was).

Manual check: launch the worktree build → Stores tab → open a scalar
store (e.g. processed backscatter, or ~/data/stores/bathymetry/chart) → Add
to map → Layers tab → right-click → Colormap range… → drag the handles
or type bounds; the map recolours live. Reset to auto returns to data-driven.

Possible follow-up (non-blocking): each drag-move calls writeSettings()
(via setRangeOverride); QSettings caches in memory so it's cheap, but a debounce
or persist-on-close could trim the churn.

The uncertainty-band default (quality palette + [0, threshold] on open) stays
a separate follow-up (needs #104 band semantics).

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Authored-By: Claude Code Agent
Model: Claude Opus 4.8

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