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_place.luau

@@ -0,0 +1,40 @@
+-- Which Studio is the bridge actually driving, and can that place be PLAYED?
+local out = {}
+local function say(s) table.insert(out, s) end
+
+say("place name: " .. tostring(game.Name))
+say("PlaceId: " .. tostring(game.PlaceId))
+say("GameId: " .. tostring(game.GameId))
+local RS = game:GetService("RunService")
+say("IsEdit: " .. tostring(RS:IsEdit()) .. "  IsRunning: " .. tostring(RS:IsRunning()) ..
+	"  IsClient: " .. tostring(RS:IsClient()) .. "  IsServer: " .. tostring(RS:IsServer()))
+
+-- Is the map present, and is there anything to actually spawn onto?
+local m = workspace:FindFirstChild("Map")
+say("workspace.Map: " .. (m and (#m:GetDescendants() .. " descendants") or "MISSING"))
+say("SpawnLocations: ")
+local spawns = 0
+for _, d in ipairs(workspace:GetDescendants()) do
+	if d:IsA("SpawnLocation") then
+		spawns += 1
+		say(("  %s at %s"):format(d:GetFullName(), tostring(d.Position)))
+	end
+end
+if spawns == 0 then say("  NONE -- a playtest has nowhere to spawn the character") end
+
+-- StarterPlayer/StarterGui presence (a play session needs these to not error)
+for _, svc in ipairs({ "StarterPlayer", "StarterGui", "StarterPack", "Players", "Lighting" }) do
+	local ok, s = pcall(function() return game:GetService(svc) end)
+	say(("service %s: %s"):format(svc, ok and "ok" or "FAIL"))
+end
+
+-- Rojo connection state: is the synced source actually in this place?
+local SS = game:GetService("ServerScriptService")
+local srv = SS:FindFirstChild("Server")
+say("ServerScriptService.Server: " .. (srv and srv.ClassName or "MISSING"))
+if srv then
+	local mb = srv:FindFirstChild("MapBuilder")
+	say("  MapBuilder present: " .. tostring(mb ~= nil))
+end
+
+return table.concat(out, "\n")