G1000: two-way sim sync, more PFD/MFD fidelity, authentic dialogs

Sync (FlyWithLua companions in plugins/ + server/fmssync.js):
- FMS flight-plan two-way sync (App <-> in-sim FMS) via fms-sync.lua
- G1000 UI-state publish (page/range/inset) via ui-sync.lua + CDI source,
  baro, map-range follow
- Terrain awareness: elevation grid probe (terrain-probe.lua) -> red/yellow
  MFD overlay vs aircraft altitude

PFD:
- AFCS mode annunciation bar from autopilot _status datarefs
- CDI source GPS/VLOC colouring, BRG1/BRG2 pointers + DME windows, marker beacons
- magenta speed/altitude trend vectors, selected-altitude alerting
- time-based (frame-rate-independent) smoothing for attitude/heading/tapes

MFD:
- nav data bar (DTK/ETE/active leg), airways overlay from earth_awy.dat,
  compass rose anchored to the ownship

Dialogs (NEAREST/FLIGHTPLAN/DIRECT-TO/PROCEDURES):
- flat, square, embedded G1000 look (no shadow/rounded/transparency)
- compact lower-right placement, no close X (softkey toggles), single window
- NEAREST 2-line entries (ILS/VFR, COM freq, runway length), PROC action menu

Service worker: network-first HTML so reloads pick up new builds (cache v2).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

plugins/terrain-probe.lua

@@ -0,0 +1,55 @@
+-- ============================================================================
+-- X-Plane Glass Cockpit  —  Terrain awareness probe  (FlyWithLua companion)
+-- ============================================================================
+-- The web MFD can't read X-Plane's scenery elevation over the Web API. This
+-- script samples a grid of terrain heights around the aircraft with X-Plane's
+-- terrain probe and writes them to terrain.json in the sync folder; the bridge
+-- streams it to the tablets, which colour it red/yellow vs aircraft altitude
+-- (G1000 TAWS). See terrain-sync in server/fmssync.js.
+--
+-- INSTALL: copy to <X-Plane>/Resources/plugins/FlyWithLua/Scripts/ (alongside
+-- fms-sync.lua). Needs FlyWithLua NG+ (XPLM scenery-probe bindings).
+-- ============================================================================
+
+local SYNC = SYSTEM_DIRECTORY .. "Output/fms-sync/"
+local OUT  = SYNC .. "terrain.json"
+os.execute('mkdir -p "' .. SYNC .. '" 2>/dev/null || mkdir "' .. SYNC .. '" 2>nul')
+
+local M_FT  = 3.28084
+local ROWS, COLS = 24, 24
+local DLAT, DLON = 0.35, 0.5          -- half-box (deg) around the aircraft
+local probe = XPLMCreateProbe(0)      -- xplm_ProbeY
+
+-- terrain elevation (ft MSL) at a lat/lon, via the vertical scenery probe
+local function elev_ft(lat, lon)
+  local x, y, z = XPLMWorldToLocal(lat, lon, 0)
+  local res, _px, py = XPLMProbeTerrainXYZ(probe, x, y, z)
+  if res ~= 0 then return 0 end                 -- 0 = xplm_ProbeHitTerrain
+  local _plat, _plon, palt = XPLMLocalToWorld(x, py, z)
+  return math.max(0, math.floor(palt * M_FT))
+end
+
+function gc_terrain_tick()
+  local lat = get("sim/flightmodel/position/latitude")
+  local lon = get("sim/flightmodel/position/longitude")
+  local alt = math.floor(get("sim/flightmodel/position/elevation") * M_FT)  -- true MSL
+  local n, s = lat + DLAT, lat - DLAT
+  local w, e = lon - DLON, lon + DLON
+  local cells = {}
+  for r = 0, ROWS - 1 do                          -- r = 0 → north (top)
+    local glat = n - (r / (ROWS - 1)) * (n - s)
+    for c = 0, COLS - 1 do                         -- c = 0 → west
+      local glon = w + (c / (COLS - 1)) * (e - w)
+      cells[#cells + 1] = elev_ft(glat, glon)
+    end
+  end
+  local f = io.open(OUT, "w")
+  if not f then return end
+  f:write(string.format(
+    '{"lat":%.5f,"lon":%.5f,"alt":%d,"n":%.5f,"s":%.5f,"w":%.5f,"e":%.5f,"rows":%d,"cols":%d,"elev":[%s]}',
+    lat, lon, alt, n, s, w, e, ROWS, COLS, table.concat(cells, ",")))
+  f:close()
+end
+
+do_often("gc_terrain_tick()")     -- ~1×/sec
+logMsg("[glass-cockpit] terrain probe active -> " .. OUT)