Add capability download and selection actions to Capabilities and SDK pages

[GsCommand]

Goal

Turn the capability model from static explanation into an actionable developer flow.

Builders should be able to:

• choose a capability
• download or copy its manifest/schema bundle reference
• copy SDK install/wrap snippets
• optionally add a capability package to a local "selection/cart" UI for future provisioning

Important framing

Do not imply paid checkout is live unless implemented.
Use language like:

• Select capability
• Add to build plan
• Download manifest
• Copy SDK snippet
• View schema bundle

Avoid premature ecommerce language unless it is clearly a future placeholder.

Pages to update

• public/capabilities.html
• public/docs/wrap-your-agent.html
• optionally public/sdk-records.html

UX model

Each capability category card should include action buttons:

1. Download manifest
2. Copy SDK snippet
3. Add to build plan

For Trust & Verification active v1, buttons should be active.
For namespace packages, buttons can be active for build-plan selection but schema download should say Manifest planned unless matching artifacts exist.

Data model

Create a lightweight static capabilities data file if helpful, for example:

public/capabilities/capabilities.v1.json

Suggested shape:

{
  "version": "1.0.0",
  "groups": [
    {
      "id": "trust-verification",
      "name": "Trust & Verification",
      "status": "v1 active",
      "capabilities": ["verify", "authenticate", "authorize", "attest", "sign", "permit", "grant", "approve", "reject", "endorse"],
      "artifacts": {
        "manifest": "/capabilities/trust-verification/manifest.json",
        "schemas": "/capabilities/trust-verification/schemas/",
        "agentCard": "/agent-cards/verifyagent.json"
      }
    }
  ]
}

Only create links to files that actually exist, or create the static files as part of the task.
Do not invent broken links.

Build-plan/cart behavior

Add a small local UI:

• clicking Add to build plan stores the group/capability in localStorage
• a small Build plan panel shows selected capabilities
• user can clear selection
• no payment processing
• no account system
• no backend

Use this language:
Build plan, not cart, until real checkout/provisioning exists.

SDK snippet behavior

For a capability like summarize, copied snippet example:

const { output, receipt } = await cl.wrap("summarize", async () => {
  return { summary: "..." };
});

For capability groups, show generic example:

const { output, receipt } = await cl.wrap("verify", async () => {
  return { verified: true };
});

Download behavior

For active Trust & Verification:

• provide a JSON manifest file or static manifest download
• include shared proof model reference
• include capability list
• include verifier endpoint references

For planned namespace packages:

• Manifest planned or Coming soon
• still allow Add to build plan

Acceptance checks

• Capability cards expose clear actions.
• No broken download links.
• Add to build plan works client-side.
• Selected capabilities persist with localStorage.
• Users are not told to download all schemas.
• Copy says: pick only capabilities your agent supports.
• No fake paid checkout.
• Existing verifier and docs still work.