feat: improve web_fetch readability extraction

package.json

@@ -142,6 +142,7 @@
     "@mariozechner/pi-ai": "0.46.0",
     "@mariozechner/pi-coding-agent": "^0.46.0",
     "@mariozechner/pi-tui": "^0.46.0",
+    "@mozilla/readability": "^0.6.0",
     "@sinclair/typebox": "0.34.47",
     "@slack/bolt": "^4.6.0",
     "@slack/web-api": "^7.13.0",
@@ -162,6 +163,7 @@
     "hono": "4.11.4",
     "jiti": "^2.6.1",
     "json5": "^2.2.3",
+    "linkedom": "^0.18.12",
     "long": "5.3.2",
     "markdown-it": "^14.1.0",
     "osc-progress": "^0.2.0",