Add socket and host flags to dev server

[silviogutierrez]

A combined batch of framework changes.

Dev server

• Build mode --socket / --host. The build-mode dev server can now bind a unix socket or an explicit host, so it can front a proxy/tunnel without owning a TCP port.
• Dedupe injected side-cars. Side-car processes injected via configuration are de-duplicated, so the same tunnel/worker is not spawned twice.

Schema generation

• Unwrap NewType fields before schema generation. A NewType identifier carries its wire type in __supertype__; unwrap it before the instance-vs-class fallback in get_field_schema, otherwise a NewType instance (not a type) falls through to __class__ — typing.NewType itself — and the generated pick_schema annotation is unbuildable for pydantic.