feat(web,myra): Deploy button for a package Myra sends as a mail attachment (CL-8474)

[TheGreatAxios]

Agents never call the hub, so creating an agent is: Myra writes the package, the person presses Deploy.

Attachment contract

A reply carrying two attachments is a deployable package:

• package.json — the manifest (presence is the marker)
• definition.json — { "name": string, "systemPrompt": string, "description"?: string }

The client renders the source tree and deploys it through the existing pipeline (agent-deploy.ts → asset, git push, POST /workflows/deployments), the same path create-agent-panel uses — so Myra never needs to know the deploy shape.

Changes

• chat/threads-api.ts: frameAttachments parses named MIME leaves out of the raw frame (name, contentType, base64-decoded text) onto chat and room turn models.
• chat/deployable-package.ts: arktype-parses the two attachments into {name, systemPrompt, description?}, or null.
• chat/message-attachments.tsx: a compact "Deploy " card with the deploy mutation, success link to the new agent's chat, and the error inline; non-deployable attachments render as a plain file list.
• useDeployAgentMutation additionally invalidates visible agents and room participants.
• Myra's prompt states the contract in two sentences; no tool lists, no hub calls.

Nothing added on the hub.

Verified

bunx tsc -p apps/web --noEmit, bun run typecheck, bun run lint, bun run fmt, apps/web build + bun test ./src (582 pass), agents/myra build.

Not verified: no live run against the hub — the deploy path itself is unchanged and already covered by the create-agent panel; the MIME attachment parse was not exercised against a real @intx/tools-mail frame.

[linear-code]

CL-8474