v0.6.2

A full-codebase reliability, correctness, and coherence pass, plus a weather-panel layer menu. It
hardens the weather overlays, the caching and history layers, the course and anchor logic, makes a
set of previously silent failures visible, and moves the weather layer toggles into a floating menu.

Changed

• The weather panel's layer toggles move from the header pill row, which ran out of room and
  truncated, into a single layers menu opened from a floating button at the upper left of the
  mini-map. The button lights and shows a count whenever layers are on, the menu groups the area
  fill and the overlays and carries the source line, and it docks as a bottom sheet on a narrow
  panel so it never covers the small map from the top. The one-tap Here conditions control stays
  in the header.

Fixed

• Pressure isobars no longer stay blank after the base map style swaps (the offline fallback or a
  style reload): the overlay rebuilds its recreated sources instead of seeing an unchanged grid.
• The in-memory cache no longer evicts a just-refreshed weather grid or tide entry before older
  ones, so a refreshed view is not dropped early and refetched.
• A corrupted or legacy profile can no longer render a chart layer transparent or broken: a
  restored opacity is clamped to a valid range, matching first-registration.
• A malformed history timestamp no longer disables gap-splitting for the rest of a 24 hour track.
• The Trends panel can tell a present-but-empty history provider from an unreachable one.
• An active course's route, next, and arrival geometry survives a cross-station activation even
  when the continuously-updating calc values stream in before the one-time hydration completes.
• A dead data link (the worker failing to load, a rejected connect) shows a "Data link failed,
  reload" indicator instead of sitting forever on a connecting state.
• One chunk-load failure no longer kills route editing for the rest of the session.
• A failed track save or delete, a refused anchor drop on a server that advertises the standard
  Anchor API, a failed user chart registration, an empty-and-failed route fetch, and a chart that
  did not sync to the server all surface an error or a log breadcrumb now instead of going silent.
• The arrival alarm is stopped on teardown, profile sync retries after a transient first failure
  instead of staying local-only for the session, and a unit preset from a previous server is
  cleared when reconnecting to a different one.
• The layer opacity slider is a full-size touch target again, panel error lines use the shared
  alarm framing, and the chart action menu supports arrow-key navigation.

Internal

• IndexedDB and local-storage degrades, and an unavailable audible alarm, now log a one-line
  breadcrumb so a field report is diagnosable.
• Shared cleanups: one safety-button gutter rule, the collision overlay on the shared layer
  helpers, the tracking token on the alarms tag, anonymous access-request fetches, named collision
  threshold constants, a once-computed day paint object, and a dropped redundant per-tick sort.
• New tests cover the stream connection and worker lifecycle, the unit conversion family, the
  anchor acknowledge escalation, client-computed course VMG and time-to-go, and several boundary
  and error paths the audit found untested.
• A shared rovingFocus arrow-key action and an overlay-backdrop utility class now back both the
  chart context menu and the new weather layers menu, replacing duplicated handlers and CSS, and
  the chart context menu moved onto the shared Escape dismiss stack. The now-unused scrollEdges
  action was removed.