Aux-lane suppression + PA geometry fixes; probe/verify tooling

MapBuilder.luau
  - Suppress the aux lane across samples 525-550 (AUX_SUPPRESS_FROM/TO),
    honoring the user's hand deletion in Studio so a rebuild no longer
    regenerates it.
  - Smoothstep the width ramp over AUX_BLEND=5 samples on each side. A hard
    cut produced a 26-stud lateral fence jog; the blend removes it.
  - DO NOT remove this suppression. Re-enabling it resurrects geometry the
    user deleted by hand.

rokit.toml
  - rojo 7.5.1 -> 7.7.0 to match the auto-updating Studio plugin.
    Server older than plugin fails the handshake with
    "attempt to index number with 'protocolVersion'".

tools/
  - 34 read-only probe/verify/capture scripts used to measure the datamodel
    instead of reasoning from source.

Verified-good baseline at this commit:
  total parts       16788
  PAWestSlip        60 segs, 34.4 deg total bend, worst 1.4, 0 kinks >5
  PAEastSlip        60 segs, 30.7 deg total bend, worst 1.3, 0 kinks >5
  AuxLane parts     30 (samples 525-550 deliberately absent)
  barrier coverage  823 samples, 0 unguarded
  fence jogs >10st  0

tools/probe_ramppath.luau

@@ -0,0 +1,104 @@
+-- What do the slip ramps ACTUALLY do? Elevation + lateral profile per segment,
+-- and do they intersect the mainline deck?
+-- The user says: "on and off ramps go to the bottom and through the highway".
+-- Measure that claim directly rather than assuming.
+local ws = game:GetService("Workspace")
+local RS = game:GetService("ReplicatedStorage")
+local Circuit = require(RS:WaitForChild("Shared"):WaitForChild("Circuit"))
+local samples = Circuit.samples
+local map = ws:FindFirstChild("Map")
+if not map then return "NOMAP" end
+
+local out = {}
+local function say(s) table.insert(out, s) end
+
+-- Collect ramp deck segments in build order.
+local ramps = {}
+for _, d in ipairs(map:GetDescendants()) do
+	if d:IsA("BasePart") then
+		local name, idx = d.Name:match("^(PA%a+Slip)_Deck_(%d+)$")
+		if name then
+			ramps[name] = ramps[name] or {}
+			table.insert(ramps[name], { i = tonumber(idx), p = d })
+		end
+	end
+end
+
+-- Nearest mainline sample + signed lateral offset for a world point.
+local function nearestSample(p)
+	local bd, bi = math.huge, -1
+	for i = 1, #samples do
+		local s = samples[i]
+		local dd = (Vector3.new(p.X, 0, p.Z) - Vector3.new(s.pos.X, 0, s.pos.Z)).Magnitude
+		if dd < bd then bd, bi = dd, i end
+	end
+	return bi, bd
+end
+local function lateralAt(i, p)
+	local n = #samples
+	local a = samples[((i - 1) % n) + 1]
+	local b = samples[(i % n) + 1]
+	local f = b.pos - a.pos
+	f = Vector3.new(f.X, 0, f.Z).Unit
+	local r = Vector3.new(-f.Z, 0, f.X)
+	local rel = Vector3.new(p.X - a.pos.X, 0, p.Z - a.pos.Z)
+	return rel:Dot(r), a.pos.Y
+end
+
+for _, name in ipairs({ "PAWestSlip", "PAEastSlip" }) do
+	local segs = ramps[name]
+	if not segs then
+		say(name .. ": MISSING")
+	else
+		table.sort(segs, function(x, y) return x.i < y.i end)
+		say(("=== %s (%d segs) ==="):format(name, #segs))
+		say("seg | rampY | deckY | dY(ramp-deck) | lateral | note")
+		local under = 0
+		for k, s in ipairs(segs) do
+			if k == 1 or k % 6 == 0 or k == #segs then
+				local si = nearestSample(s.p.Position)
+				local lat, deckY = lateralAt(si, s.p.Position)
+				local dy = s.p.Position.Y - deckY
+				local note = ""
+				-- |lateral| < 30 means it is horizontally UNDER/INSIDE the deck slab.
+				if math.abs(lat) < 30 then
+					note = (math.abs(dy) < 8) and "*** THROUGH DECK ***" or "under/over deck footprint"
+				end
+				say(("%3d | %6.1f | %6.1f | %+7.1f | %+7.1f | %s")
+					:format(s.i, s.p.Position.Y, deckY, dy, lat, note))
+			end
+			local si = nearestSample(s.p.Position)
+			local lat = lateralAt(si, s.p.Position)
+			if math.abs(lat) < 30 then under += 1 end
+		end
+		say(("%s: %d/%d segments sit within the deck footprint (|lateral| < 30)")
+			:format(name, under, #segs))
+	end
+end
+
+-- Does any ramp part actually overlap a Road part in 3D?
+local roads = {}
+for _, d in ipairs(map:GetDescendants()) do
+	if d:IsA("BasePart") and d.Name:match("^Road_%d+$") then
+		table.insert(roads, d)
+	end
+end
+local clashes, tested = {}, 0
+for _, name in ipairs({ "PAWestSlip", "PAEastSlip" }) do
+	for _, s in ipairs(ramps[name] or {}) do
+		for _, r in ipairs(roads) do
+			tested += 1
+			local d = s.p.Position - r.Position
+			local sx = (s.p.Size.X + r.Size.X) / 2
+			local sy = (s.p.Size.Y + r.Size.Y) / 2
+			local sz = (s.p.Size.Z + r.Size.Z) / 2
+			if math.abs(d.X) < sx and math.abs(d.Y) < sy and math.abs(d.Z) < sz then
+				table.insert(clashes, ("%s x %s (dY=%.1f)"):format(s.p.Name, r.Name, d.Y))
+			end
+		end
+	end
+end
+say(("ramp-vs-road AABB tests: %d, overlaps: %d"):format(tested, #clashes))
+for k = 1, math.min(#clashes, 12) do say("  " .. clashes[k]) end
+if tested == 0 then say("CONTROL FAIL: nothing tested") end
+return table.concat(out, "\n")