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_after.luau

@@ -0,0 +1,73 @@
+-- The rebuild was interrupted mid-flight; its effect is UNKNOWN. Establish
+-- ground truth before touching anything else.
+--   (a) Did the build run? part count vs 16714 (user-edited) / 16820 (source).
+--   (b) Is the aux lane back? user's edited workspace had 30 aux parts,
+--       source produces 52 -- so they deleted ~22.
+--   (c) Did the smoothing pass actually land on the east slip?
+local out = {}
+local function say(s) table.insert(out, s) end
+
+local map = workspace:FindFirstChild("Map")
+if not map then return "workspace.Map MISSING" end
+
+local parts = 0
+for _, d in ipairs(map:GetDescendants()) do
+	if d:IsA("BasePart") then parts += 1 end
+end
+say(("parts=%d   (16714=user-edited, 16820=source rebuild)"):format(parts))
+
+-- Aux lane inventory, with index range + position so I can tell WHICH lane.
+local aux = {}
+for _, d in ipairs(map:GetDescendants()) do
+	if d:IsA("BasePart") then
+		local k = d.Name:match("^AuxLane_(%d+)$")
+		if k then table.insert(aux, { i = tonumber(k), p = d.Position, inst = d }) end
+	end
+end
+table.sort(aux, function(a, b) return a.i < b.i end)
+say(("AuxLane parts=%d   (30=after user deletion, 52=source)"):format(#aux))
+if #aux > 0 then
+	-- group into contiguous runs so each physical lane shows up separately
+	local runs, cur = {}, nil
+	for _, a in ipairs(aux) do
+		if cur and a.i - cur.last <= 2 then cur.last = a.i; cur.n += 1
+		else
+			if cur then table.insert(runs, cur) end
+			cur = { first = a.i, last = a.i, n = 1, p = a.p }
+		end
+	end
+	if cur then table.insert(runs, cur) end
+	for _, r in ipairs(runs) do
+		say(("   aux run idx %d..%d  n=%d  at (%.0f,%.0f,%.0f)"):format(
+			r.first, r.last, r.n, r.p.X, r.p.Y, r.p.Z))
+	end
+end
+
+-- Slip smoothness: did the relaxation take effect?
+for _, s in ipairs({ "PAWestSlip", "PAEastSlip" }) do
+	local segs = {}
+	for _, d in ipairs(map:GetDescendants()) do
+		if d:IsA("BasePart") then
+			local k = d.Name:match("^" .. s .. "_Deck_(%d+)$")
+			if k then table.insert(segs, { i = tonumber(k), p = d.Position, cf = d.CFrame }) end
+		end
+	end
+	table.sort(segs, function(a, b) return a.i < b.i end)
+	if #segs == 0 then say(s .. ": ABSENT") continue end
+	local total, worst, worstAt, over = 0, 0, -1, 0
+	for j = 2, #segs do
+		local a, b = segs[j - 1].cf.LookVector, segs[j].cf.LookVector
+		local d = math.deg(math.acos(math.clamp(a:Dot(b), -1, 1)))
+		total += d
+		if d > worst then worst = d; worstAt = segs[j].i end
+		if d > 5 then over += 1 end
+	end
+	local topY, level = segs[1].p.Y, 0
+	for _, sg in ipairs(segs) do
+		if math.abs(sg.p.Y - topY) < 0.5 then level += 1 else break end
+	end
+	say(("%s: segs=%d total=%.1fdeg worst=%.1f@%d over5=%d level=%d"):format(
+		s, #segs, total, worst, worstAt, over, level))
+end
+
+return table.concat(out, "\n")