feat: WebMCP polyfill — register skills tools with navigator.modelContext

[dfinityianblenke]

Summary

Registers list_skills, get_skill, and search_skills with navigator.modelContext so AI agents can call them as tools from any browser — Chrome 146+ natively, all others via the inline polyfill.

Two changes:

public/webmcp-setup.js — self-contained polyfill + tool registration

• Installs a navigator.modelContext shim if the native API is absent (non-Chrome-146+)
• Registers the three tools using the site's existing /.well-known/skills/ static endpoints — zero new dependencies, works right now
• execute() implementations use plain fetch(): no @dfinity/agent, no bundler, no CDN
• When PR feat: skills canister — list_skills, get_skill, search_skills #148 is deployed and @dfinity/webmcp is published to npm, the execute() bodies can be upgraded to full ICWebMCP canister calls with certified responses

src/layouts/BaseLayout.astro — two additions

• <link rel="modelcontext" href="/.well-known/webmcp.json"> — tells Chrome 146+ where to find the manifest (from PR feat: serve /.well-known/webmcp.json — WebMCP manifest endpoint #149)
• <script src="/webmcp-setup.js" defer> — loads the polyfill on every page

How the three tools work today (static API):

Tool	Implementation
list_skills	GET /.well-known/skills/index.json
get_skill(name)	GET /.well-known/skills/{name}/SKILL.md
search_skills(query)	filter on index.json by name + description

Upgrade path (post PR #148 + npm publish):

const { installPolyfill, ICWebMCP } = await import('@dfinity/webmcp');
installPolyfill();
const webmcp = new ICWebMCP({ manifestUrl: '/.well-known/webmcp.json' });
await webmcp.registerAll(); // uses Candid query calls with certified responses

Test plan

• npm run build passes (verified locally)
• <link rel="modelcontext"> and <script src="/webmcp-setup.js"> present in built HTML
• In Chrome 146+ DevTools: navigator.modelContext is the native object; webmcp-setup.js still runs but polyfill install is skipped
• In Firefox/Safari: navigator.modelContext._registry has three tools registered after page load
• navigator.modelContext._registry.get('list_skills').execute() returns the skills index
• navigator.modelContext._registry.get('get_skill').execute({name:'motoko'}) returns SKILL.md content

This optionally (but ideally) extends PR #149, and that should be merged first, which also depends on PR #148

[github-actions]

Skill Validation Report

No skill files were changed in this PR — validation skipped.