feat: Real Vercel deployment behind Publish button

[Delqhi]

Problem

The Publish button in the workspace header (WorkspaceHeader component) is currently a no-op. Clicking it does nothing. The user expects to deploy the generated application to a live URL, just like v0 does.

Goal

Implement real Vercel deployment integration behind the Publish button. When a user clicks Publish, the system should:

1. Build the target application (the one the agent is working on)
2. Create a Vercel deployment
3. Show deployment status in the UI
4. Provide a live preview URL

Acceptance Criteria

• Clicking Publish triggers a Vercel deployment
• Deployment status is shown (building, ready, error)
• Live URL is displayed and copyable
• Deployment history is tracked per workspace
• Environment variables can be configured per deployment
• Production vs Preview deployments are distinguishable
• Deploy button works from both Preview tab and Design mode

Files to modify / create

New files

lib/vercel/client.ts                # Vercel API client (REST API wrapper)
lib/vercel/deploy.ts                # Deployment logic: build → create deployment
app/api/workspace/deploy/route.ts   # POST /api/workspace/deploy — trigger deployment
app/api/workspace/deployments/route.ts # GET /api/workspace/deployments — list history
components/workspace/deploy-status.tsx # Deployment status indicator (spinner, progress, URL)
components/workspace/deploy-history.tsx # List of past deployments

Files to modify

components/workspace/workspace-header.tsx   # Wire onPublish to real deployment API
components/workspace/preview-panel.tsx      # Add deploy button or status overlay
components/workspace/workspace.tsx          # Pass deployment state through

Technical Notes

• Vercel API requires VERCEL_TOKEN environment variable
• Use the vercel npm package or direct REST API calls
• Build process: The target app (in SIN_WORKSPACE_DIR) must be built (e.g., next build or npm run build)
• Deployment target: Either Vercel CLI (vercel --yes) or API (POST /v13/deployments)
• The deployment should include the built output, not the source code
• Store deployment metadata (URL, status, createdAt) in .sin-webui/deployments.json

Out of Scope (per AGENTS.md)

This feature is explicitly listed as "out of scope" in AGENTS.md: "Real Vercel deploys go through Docker + Cloudflare Tunnel (see PLAN_DEPLOY.md)." This issue supersedes that decision for users who want Vercel integration.

Related

• AGENTS.md §8: Real Vercel-Deploy is out of scope (Docker + Cloudflare Tunnel preferred)
• PLAN_DEPLOY.md: Existing self-hosting guide
• components/workspace/workspace-header.tsx: Publish button (currently no-op)

[Delqhi]

Implemented and merged to main via #58 (commit 30de716) and prior PRs (#56).

Includes:

• lib/vercel/client.ts — Vercel API REST wrapper
• lib/vercel/deploy.ts — Deployment logic with SHA1-dedup file upload
• app/api/workspace/deploy/route.ts — POST to trigger Vercel deployment
• app/api/workspace/deployments/route.ts — GET list of past deployments
• components/workspace/deploy-status.tsx + deploy-history.tsx — UI for status + history
• Wired Publish button to real /api/workspace/deploy endpoint

Verification: Build succeeds. Routes are live. Requires VERCEL_TOKEN env var at runtime to actually deploy.