feat: add remote HTTP MCP federation

[lalalic]

Objective

Add provider-agnostic remote HTTP MCP federation so Mac Developer Bridge can act as a single MCP gateway for existing remote/local MCP servers such as NeoX.

Scope

• Add generic transport: "http" providers with static MCP URLs.
• Add generic Bonjour discovery for dynamic LAN endpoints.
• Preserve existing stdio provider behavior.
• Normalize child tool names to portable parent aliases while preserving routing to the original child name.
• Detect alias collisions deterministically.
• Keep remote provider failures isolated so native bridge tools and other providers stay available.
• Add focused HTTP federation fixtures/tests and operator documentation.

Non-goals

• No NeoX-specific runtime code.
• No bulk /files/ proxy or LAN media relay through Mac Developer Bridge.
• No dependency on or copy of unmerged PR feat: federate MCP resources and UI metadata #17 resource/UI federation changes.
• No public exposure of child LAN endpoints.

Acceptance criteria

• Existing stdio federation remains compatible.
• Static HTTP MCP discovery and tool calls work.
• media.search can be exposed as a portable alias such as neox_phone__media_search and routes back to media.search.
• Alias collisions reject the provider rather than routing ambiguously.
• A remote HTTP provider can fail and recover without restarting Mac Developer Bridge or blocking other providers.
• Bonjour can resolve a current host/port instead of hard-coding a DHCP address.

Validation

• npm run check
• node tests/federation.mjs

Both pass locally on the PR head.

Merge policy

Ask before merge.

[lalalic]

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