feat: add WebMCP polyfill — navigator.modelContext tools for AI agents

Registers list_skills, get_skill, and search_skills with
navigator.modelContext so AI agents can call them as tools regardless of
browser: Chrome 146+ uses the native WebMCP API, all others pick up the
inline polyfill installed by this script.

- public/webmcp-setup.js — self-contained polyfill + tool registration
  Uses the existing /.well-known/skills/ static API endpoints (no canister
  or @dfinity/webmcp dependency required). When PR #148 is deployed and
  @dfinity/webmcp is published, the execute() functions can be upgraded to
  use ICWebMCP for full Candid canister calls with certified responses.

- src/layouts/BaseLayout.astro
  <link rel="modelcontext" href="/.well-known/webmcp.json"> — signals
  Chrome 146+ to load the manifest automatically.
  <script src="/webmcp-setup.js" defer> — loads the polyfill on every page.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: dfinityianblenke

public/webmcp-setup.js

@@ -0,0 +1,123 @@
+/**
+ * IC Skills WebMCP setup — registers list_skills, get_skill, and search_skills
+ * with navigator.modelContext so AI agents (Chrome 146+, @dfinity/webmcp
+ * polyfill, WebMCP-aware browser extensions) can call them as tools.
+ *
+ * This script uses the site's existing /.well-known/skills/ static endpoints,
+ * so it works without a deployed skills canister. When the skills canister
+ * (PR #148) is deployed and @dfinity/webmcp is published to npm, this script
+ * can be replaced with the full ICWebMCP integration from webmcp.json.
+ *
+ * Discovery: <link rel="modelcontext" href="/.well-known/webmcp.json"> in the
+ * page head signals Chrome 146+ to load the manifest automatically.
+ */
+(function () {
+  "use strict";
+
+  // Install navigator.modelContext polyfill for non-Chrome-146+ environments.
+  if (typeof navigator !== "undefined" && !navigator.modelContext) {
+    var _registry = new Map();
+    Object.defineProperty(navigator, "modelContext", {
+      value: {
+        registerTool: function (tool) {
+          _registry.set(tool.name, tool);
+          return Promise.resolve();
+        },
+        unregisterTool: function (name) {
+          _registry.delete(name);
+          return Promise.resolve();
+        },
+        _registry: _registry,
+      },
+      writable: true,
+      configurable: true,
+    });
+  }
+
+  if (typeof navigator === "undefined" || !navigator.modelContext) return;
+
+  var ctx = navigator.modelContext;
+
+  ctx.registerTool({
+    name: "list_skills",
+    description:
+      "List all available Internet Computer skill topics with their " +
+      "names, titles, descriptions, and categories.",
+    inputSchema: {
+      type: "object",
+      properties: {},
+      additionalProperties: false,
+    },
+    execute: function () {
+      return fetch("/.well-known/skills/index.json").then(function (r) {
+        return r.json();
+      });
+    },
+  });
+
+  ctx.registerTool({
+    name: "get_skill",
+    description:
+      'Get the full documentation for a specific IC skill by name ' +
+      '(e.g. "motoko", "asset-canister", "internet-identity"). ' +
+      "Returns the complete SKILL.md content. Returns null if not found.",
+    inputSchema: {
+      type: "object",
+      properties: {
+        name: {
+          type: "string",
+          description:
+            'Skill name in lowercase-hyphenated format, ' +
+            'e.g. "motoko", "ckbtc", "https-outcalls", "webmcp"',
+        },
+      },
+      required: ["name"],
+      additionalProperties: false,
+    },
+    execute: function (params) {
+      var url =
+        "/.well-known/skills/" +
+        encodeURIComponent(params.name) +
+        "/SKILL.md";
+      return fetch(url).then(function (r) {
+        return r.ok ? r.text() : null;
+      });
+    },
+  });
+
+  ctx.registerTool({
+    name: "search_skills",
+    description:
+      "Search Internet Computer skill documentation by keyword. " +
+      "Matches against skill names and descriptions. " +
+      "Returns summaries of matching skills.",
+    inputSchema: {
+      type: "object",
+      properties: {
+        query: {
+          type: "string",
+          description: "Keyword to match against skill names and descriptions",
+        },
+      },
+      required: ["query"],
+      additionalProperties: false,
+    },
+    execute: function (params) {
+      return fetch("/.well-known/skills/index.json")
+        .then(function (r) {
+          return r.json();
+        })
+        .then(function (data) {
+          var q = String(params.query).toLowerCase();
+          return {
+            skills: data.skills.filter(function (s) {
+              return (
+                s.name.toLowerCase().includes(q) ||
+                s.description.toLowerCase().includes(q)
+              );
+            }),
+          };
+        });
+    },
+  });
+})();

src/layouts/BaseLayout.astro

@@ -73,6 +73,7 @@ const defaultJsonLd = JSON.stringify({
   <meta name="twitter:image" content={ogImage}>
 
   <link rel="alternate" type="text/plain" title="LLMs.txt" href="/llms.txt">
+  <link rel="modelcontext" href="/.well-known/webmcp.json">
 
   <meta name="theme-color" content="#000000">
   <link rel="icon" type="image/svg+xml" href="/favicon.svg">
@@ -86,6 +87,7 @@ const defaultJsonLd = JSON.stringify({
   <link href="https://fonts.googleapis.com/css2?family=Inter:wght@300;400;600;700&family=JetBrains+Mono:wght@400;700&display=swap" rel="stylesheet">
 
   <script is:inline src="/matomo.js" async></script>
+  <script is:inline src="/webmcp-setup.js" defer></script>
 </head>
 <body>
   <script is:inline>