v0.3.0

K4 Remote v0.3.0

Mode-aware panadapter, ATU/TUNE control, update check, control tooltips.

Panadapter (FR-PAN-05..09)
  - Click-to-QSY places the passband by sideband sense: USB/DATA anchor
    its low edge on the click, LSB/DATA-REV its high edge, CW/AM/FM its
    centre. Confirmed on a real K4.
  - The waterfall scrolls with the VFO instead of smearing: each row is
    pinned to the frequencies it was sampled at.
  - Frequency-labelled axis and a span / Hz-per-bin readout; the level
    window follows the radio's #REF and #SCL.
  - Bins are cropped from the streamed tier to the #SPN window, which
    also raises horizontal resolution at no memory cost.
  - The waterfall is drawn as one texture rather than ~12k rectangles
    per pane per frame.

ATU and TUNE (FR-ATU-01, FR-TX-TUNE-01, closes #118)
  Arm-gated like voice and CW, deliberately kept out of the microphone
  path, and ended by both the emergency stop and the link-loss
  fail-safe.

Also
  - About-box update check against the GitHub releases API, operator-
    initiated only (FR-UI-UPD-01).
  - Switchable control tooltips naming each control's CAT command, 55 of
    67 wired (FR-UI-TIP-01).
  - Fixed: the MiniPAN header size, which prevented the mini-pan from
    ever displaying; and the silently dropped #REF$ / #SPN$ read-back.
  - CI runs cross-platform builds only on a release tag.

214 tests. Gate green on Linux x86_64 + arm64, macOS and Windows.

Evidence: panadapter click-to-QSY is field-verified against a real K4.
Waterfall scrolling, the axis/level scales, the rasterised waterfall,
TU3 completion behaviour and the update check's live request are
unit-test and simulator evidence only.