Experiment: migrate web build to vite-plus 1.3.0

- vp migrate rewrote scripts (vite build -> vp build), aliased vite to
  @voidzero-dev/vite-plus-core 1.3.0 with an overrides pin, and switched
  the config import to vite-plus.
- Manual one-line fix migrate missed: minify "esbuild" -> true (Vite 8
  dropped bundled esbuild; oxc minifier is the replacement).
- Widened cleanStaleChunks sweep from .js/.js.map to .css/.mjs too:
  Rolldown renames emitted css chunks, and two stale vite-7-era css
  files (annotation_layer_builder, text_layer_builder) survived the
  old js-only regex.
- Verified: both custom plugins survive; prod/dev/watch builds OK;
  two consecutive builds idempotent at 289 files; vendor/pdfjs assets
  byte-identical; entry names (main.js/reader.js) unchanged.

package.json

@@ -5,9 +5,9 @@
   "scripts": {
     "build:css": "tailwindcss -i ./web/static/input.css -o ./web/static/style.css --watch",
     "build:css:prod": "tailwindcss -i ./web/static/input.css -o ./web/static/style.css --minify",
-    "build:ts": "cp node_modules/htmx.org/dist/htmx.min.js web/static/htmx.min.js && vite build",
-    "build:ts:dev": "cp node_modules/htmx.org/dist/htmx.min.js web/static/htmx.min.js && vite build --mode development",
-    "build:ts:watch": "cp node_modules/htmx.org/dist/htmx.min.js web/static/htmx.min.js && vite build --watch",
+    "build:ts": "cp node_modules/htmx.org/dist/htmx.min.js web/static/htmx.min.js && vp build",
+    "build:ts:dev": "cp node_modules/htmx.org/dist/htmx.min.js web/static/htmx.min.js && vp build --mode development",
+    "build:ts:watch": "cp node_modules/htmx.org/dist/htmx.min.js web/static/htmx.min.js && vp build --watch",
     "build": "npm run build:ts && npm run build:css:prod",
     "dev": "npm run build:ts:dev && npm run build:css"
   },
@@ -34,6 +34,10 @@
     "playwright": "^1.64.1",
     "tailwindcss": "^3.4.19",
     "typescript": "^5.9.3",
-    "vite": "^7.3.1"
+    "vite": "npm:@voidzero-dev/vite-plus-core@1.3.0",
+    "vite-plus": "1.3.0"
+  },
+  "overrides": {
+    "vite": "npm:@voidzero-dev/vite-plus-core@1.3.0"
   }
 }