chore: bump version to 1.4.0, document cooldown probing and elastic pools

README: new "冷却与半冷却探测（自愈调度）" section with the per-class cooldown
table (5xx exponential to 5min / 401-403 10min / 429 30s fixed / quota aligned
to its window), the probe-slot formula and the ordering rule that probes are
tried last. The LuaJIT section now says the pool is an elastic ceiling rather
than a preallocation and documents both step formulas. Headline figures replaced
with measured ones: idle ~10 MB, ~19 MB starting with a 29 MB audit log, and a
new bullet for on-demand log loading.

package.json also loses a `\u2014` escape and the broken indentation that an
earlier edit left in the electron-builder block.

cmd/gui/package.json

@@ -1,6 +1,6 @@
 {
   "name": "modelrouter-gui",
-  "version": "1.2.0",
+  "version": "1.4.0",
   "description": "ModelRouter Desktop — embedded ModelRouter core with tray",
   "author": "ModelRouter",
   "main": "main.js",
@@ -22,7 +22,7 @@
   "build": {
     "appId": "com.modelrouter.gui",
     "productName": "ModelRouter",
-"linux": {
+    "linux": {
       "target": [
         "deb",
         "rpm",
@@ -32,9 +32,9 @@
       "icon": "build/icon.png",
       "maintainer": "ModelRouter",
       "synopsis": "ModelRouter Desktop",
-"desktop": {
+      "desktop": {
         "entry": {
-            "StartupWMClass": "modelrouter-gui"
+          "StartupWMClass": "modelrouter-gui"
         }
       },
       "extraResources": [