…gionsForBand (#3060). Principle IV.

PR #3050 (closing #2649) added a license-class-aware overload of
BandPlanManager::contiguousRegionsForBand that filters segments by the
operator's class before merging contiguous regions. The filter-BEFORE-merge
ordering is load-bearing: if an allowed segment is adjacent to a disallowed
one, they must NOT merge — otherwise the merged region's center could fall
on a disallowed frequency. The implementation comment calls this out, but
no test pinned the invariant. A future refactor (STL-algorithm
consolidation, parallelisation of the segment loop) could silently
re-introduce the bug.

This commit adds tests/band_plan_license_filter_test.cpp covering the five
scenarios enumerated in the issue:

  1. Empty class → no filter (three-arg with "" == two-arg).
  2. Empty-license segments (BCN markers) always pass.
  3. Class filter drops non-matching segments [E]/[G]/[E,G] under T/G/E.
  4. Adjacent allowed/disallowed segments stay separate (THE invariant).
  5. Trailing-whitespace allowedClass is trimmed; "GE" doesn't match
     "G,E" substring-style; lowercase doesn't match uppercase.

To make scenario 5 pass and to keep the comparison symmetric, the
allowedClass argument is now .trimmed() at the top of the filter — the
segment-side code was already trimmed per element. This is a one-line
forgiveness fix; existing callers that pass already-trimmed strings
(MainWindow::startSwrSweep, AtuPreTuneDialog::populateBands) are
unaffected.

A small public test hook BandPlanManager::setSegmentsForTest is added
so the test can inject synthetic segments without going through resource
loading or AppSettings. Matches the *ForTest naming convention already
used in PerfTelemetry::resetForTest and
AetherAx25LibmodemShim::processRecoveredBitsForTest.

Honors Principle IV (region-aware data comes from BandPlanManager, not
BandDefs.h) by hardening the regression-guard around the manager's
license-class filter — exactly the surface a refactor cleanup pass would
be tempted to consolidate.

Blast radius: risk_score=0.198, 4 high-risk affected (top: MainWindow::MainWindow, MainWindow::buildMenuBar, MainWindow::buildUI). Header change is purely additive (new public inline setSegmentsForTest) — no existing API touched; the high-risk callers don't reference the new symbol and aren't behaviorally affected, only a recompile cascade. The .cpp change adds .trimmed() to one argument — forgiveness-only (strings that previously failed strict comparison may now match); no caller currently passes whitespace.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

BandPlanManager.h:4 includes <QColor> for the Segment struct's color
field.  The test target was only linking Qt6::Core, so the test build
failed with `fatal error: QColor: No such file or directory`.

Fix: add Qt6::Gui to target_link_libraries.  Local build clean, all 13
test scenarios pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>