feat: `vouch serve --transport http` + Bearer-token auth [VEP]

[plind-junior]

Labels: enhancement, VEP

What you're trying to do

vouch serve today is stdio + JSONL only, so vouch can't run as a network MCP server. As a result, five Claude surfaces are blocked: Claude.ai web Custom Connectors, Claude mobile (write), Claude Managed Agents, the Messages-API mcp_servers field, and Anthropic Computer Use. They each require a publicly reachable HTTPS MCP endpoint, and vouch has nothing to point at.

This is the single highest-leverage change. ROADMAP 0.1 already scopes it.

Suggested shape

vouch serve --transport http \
            --bind 127.0.0.1:7777 \
            --auth bearer

• New module src/vouch/http_server.py wraps the same kb.* handlers as jsonl_server.py but speaks MCP-over-Streamable-HTTP (per the official MCP spec).
• Auth: read bearer_tokens: [...] (or bearer_token: env:VOUCH_TOKEN) from config.yaml under a new serve section; reject unauthenticated requests with HTTP 401.
• Defaults: bind 127.0.0.1, refuse to start unbound (0.0.0.0) without an explicit auth config.
• Ship a reference deployment under adapters/http-tunnel/: Dockerfile + fly.toml + a Cloudflare Tunnel compose.yml.

Acceptance

• vouch serve --transport http exposes the full kb.* method surface as a Custom Connector that Claude.ai can register.
• Without a Bearer token, requests return 401; with a valid token, behavior matches stdio/JSONL.
• A test pack from vouchdev/setup-vouch (or curl) hits /health and /messages end-to-end.
• Default bind is localhost; --bind 0.0.0.0 errors out unless --auth bearer is set.

Out of scope

• Multi-tenancy / mapping Bearer tokens to scoped views (depends on chore(deps): bump actions/checkout from 4 to 6 #2).
• OAuth — Bearer is the v1 surface.
• TLS termination (do it at the tunnel/Cloudflare/proxy layer).