Daikoku PA: lift mainline over the apron, rebuild both ramps

The PA ring road and the expressway mainline were both at ground level, so
the ring parapet stood INSIDE the carriageway (measured -10.0 studs of
vertical overlap: a wall in the middle of the road).

Reference photos of the real Daikoku Futo PA show the expressway flying
OVER the parking apron on pillars, with the PA at ground level and ramps
climbing up to meet it. Rebuilt to match:

- mainline lifted 38 studs through the junction, eased in/out (max 5.26%
  grade, within real expressway limits)
- PA ring + apron stay at ground level; legacy PARingPillar props removed
- both on/off ramps regraded over the full rise with smoothstep easing,
  segments overlapped 3 studs so wheels can't catch a seam, plus support
  pillars and edge kerbs where the deck is high

Verified in-engine against built parts (tools/diag_daikoku.luau), not just
source: clearance now +28.0 studs, both ramps continuous (max step 5.62,
no gaps). tools/plot_daikoku.py renders the plan/section for comparison.

tools/verify_push.luau

@@ -0,0 +1,90 @@
+--[[
+	verify_push.luau -- verify a push by INSPECTING THE DATAMODEL, not by
+	trusting push_module.py's self-report.
+
+	push_module.py reported "assembled=39591 expected=39591 match=true" while
+	the live module was in fact 30631 bytes with no _buildForDiag. That check
+	only proves the script reassembled its own chunks correctly client-side;
+	it does not prove the DataModel accepted the write. This closes that gap.
+
+	Reports, for every CarManager in ServerScriptService:
+	  * instance count (must be 1 -- diagnostic clones caused duplicates)
+	  * Source length vs the expected 39591
+	  * presence of marker strings that only exist in the new source
+	  * the module's exported key set after a fresh require
+]]
+
+local ServerScriptService = game:GetService("ServerScriptService")
+
+local EXPECTED_LEN = 41650
+local MARKERS = {
+	"SHELL_YAW_OVERRIDE",
+	"bestVol",
+	"_buildForDiag",
+}
+
+local out = {}
+local function log(...)
+	local parts = {}
+	for i = 1, select("#", ...) do
+		parts[#parts + 1] = tostring((select(i, ...)))
+	end
+	table.insert(out, table.concat(parts, " "))
+end
+
+local mods = {}
+for _, d in ipairs(ServerScriptService:GetDescendants()) do
+	if d:IsA("ModuleScript") and d.Name == "CarManager" then
+		mods[#mods + 1] = d
+	end
+end
+
+log(string.format("CarManager instances: %d  %s", #mods, #mods == 1 and "OK" or "*** should be exactly 1 ***"))
+
+for i, m in ipairs(mods) do
+	local src = nil
+	pcall(function()
+		src = m.Source
+	end)
+	if not src then
+		log(string.format("  [%d] %s  <source unreadable>", i, m:GetFullName()))
+	else
+		log(string.format("  [%d] %s", i, m:GetFullName()))
+		log(
+			string.format(
+				"      length %d vs expected %d   %s",
+				#src,
+				EXPECTED_LEN,
+				#src == EXPECTED_LEN and "MATCH" or "*** STALE / MISMATCH ***"
+			)
+		)
+		for _, mk in ipairs(MARKERS) do
+			log(string.format("      marker %-26s %s", mk, src:find(mk, 1, true) and "present" or "*** MISSING ***"))
+		end
+	end
+end
+
+if #mods == 1 then
+	log("")
+	local ok, mod = pcall(require, mods[1])
+	if ok and typeof(mod) == "table" then
+		local keys = {}
+		for k in pairs(mod) do
+			keys[#keys + 1] = tostring(k)
+		end
+		table.sort(keys)
+		log("require() keys: " .. table.concat(keys, ", "))
+		log(
+			"_buildForDiag:  "
+				.. typeof(mod._buildForDiag)
+				.. (
+					typeof(mod._buildForDiag) == "function" and "   <- new source IS live"
+					or "   <- STILL RUNNING OLD CODE (require cache from Play start)"
+				)
+		)
+	else
+		log("require failed: " .. tostring(mod))
+	end
+end
+
+return table.concat(out, "\n")