feat(spothub): column-visibility menu + shrinkable width (#4157)

[M7HNF-Ian]

Closes #4157.

What

• Right-click the Spot List column header for a checkable menu that
  hides/shows Comment, Spotter, Band, Mode, Source. Time, Freq, and
  DX Call stay always-on. Hidden state persists in AppSettings and
  restores on next SpotHub open.
• Dialog's setMinimumSize width floor lowered from 680 to 360, so
  the window can be dragged narrower once columns are hidden. The
  other tabs keep their own natural minimums via Qt's layout
  constraints — this only removes the hard-coded override.
• Band-filter checkboxes switched from an equal-stretch QHBoxLayout
  to a wrapping flow layout, so the checked/unchecked state stays
  legible at narrow widths instead of compressing illegibly.

Test plan

• Built and ran locally against a live DX cluster feed
• Hid/showed each toggleable column via the header menu — table
  reflows correctly, last visible column absorbs the freed width
• Closed and reopened SpotHub — hidden-column state persisted
• Dialog drags narrower once columns are hidden
• Band-filter checkboxes stay clearly readable at narrow widths

[jensenpat]

Holding for next week's release

[aethersdr-agent]

Nice, self-contained feature — thanks for this, @M7HNF-Ian. The column-visibility menu, the persist/restore loop, and the wrapping band-filter layout all read cleanly and match the surrounding SpotHub style. I checked the parts most likely to bite: BandFilterProxy only overrides filterAcceptsRow, so columns map 1:1 and driving setColumnHidden() with source-column enums is correct; setChecked() is called before the QAction::toggled connect, so restoring the menu state doesn't spurious-save; and the FlowLayout is the canonical Qt example with proper item ownership in the dtor (no leak). The 360px width floor is also safe in practice — the Display tab's fixed-width (90px) toggles already enforce a wider layout minimum, so those tabs can't actually shrink past their content.

One convention item to reconcile, otherwise this looks good to merge.

Would like reconciled before merge (or explicitly waived)

• Principle V: the 5 new column-visibility settings are flat keys (SpotListColVisible_*); new features are supposed to persist as one nested-JSON object under a single root key. See inline — noting the whole dialog is already flat, so this may be a deliberate consistency call on your/the maintainer's part.

Non-blocking notes

• Worth a quick manual check that the Display/Settings tabs still look right when dragged toward the new 360px floor (I believe they're protected by their own layout minimums, but eyes-on is cheap).

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_{🤖 aethersdr-agent · cost: $3.4240 · model: claude-opus-4-8}

[aethersdr-agent]

Per Principle V (see the PR template checklist and .specify/memory/constitution.md), new features should persist as a single nested-JSON value under one root key rather than adding flat keys — here that's 5 new top-level keys (SpotListColVisible_Comment, _Spotter, …). Something like a single SpotListColumnVisibility key holding {"Comment": true, "Spotter": false, …} would keep the settings surface tidy and match the convention for new persistence.

That said, the entire DxClusterDialog (and the adjacent band-filter code you touched) already uses flat keys, so a lone nested key here would be locally inconsistent. Reasonable to either follow Principle V for the new feature or deliberately match the surrounding flat style — flagging so it's a conscious choice rather than an oversight.

[ten9876]

First-pass triage review (not exhaustive — surfacing blockers to keep this moving):

Blockers

None spotted in a first pass. Verified the load-bearing details:

• SpotTableModel::Column (DxClusterDialog.h:38) is { ColTime, ColFreq, ColDxCall, ColComment, ColSpotter, ColBand, ColMode, ColSource, ColCount }. The kToggleCols set is exactly the five non-core columns, with Time/Freq/DX Call always-on — so even hiding every toggleable column leaves 3 columns visible, no all-hidden layout break, and no off-by-one on the indices.
• The view is driven through m_proxyModel (QSortFilterProxyModel, DxClusterDialog.cpp:1870/1899). Since that proxy maps columns 1:1, using source-model column indices with m_spotTable->setColumnHidden() is correct.
• Restore runs after setModel, defaults to "True" (new users see all columns), and persists on toggle via AppSettings — model/view/settings stay in sync.

Secondary notes

• setMinimumSize(680,560) → setMinimumSize(360,560) lowers the width floor for the whole dialog, not just the Spot List tab. The PR body says the other tabs enforce their own minimums via layout constraints; worth a quick eyeball that Connections/Settings/etc. don't visually squish at 360px, since a hard floor was the only thing guaranteeing it before (couldn't verify without building).
• FlowLayout is a faithful copy of the standard Qt flow-layout example and relies on heightForWidth propagating up through the enclosing QVBoxLayout — normally fine, just confirm the wrapped band-filter row actually gets the extra vertical space when it wraps at narrow widths (your test plan says it does).

Nice, self-contained change — looks good to me on a first pass.