Move the Mini App connector onto the IPC channel #259

Parent

#251

What to build

A Mini App's tool calls travel on the parent/child IPC channel beside lifecycle messages, so the
plugin's own logging can no longer corrupt the protocol or abort its runtime.

Acceptance criteria

• Tool listing and calling behave as before, including the credential scope, the provider allowlist
  and the schema-checked argument call.
• A plugin writing to stdout or stderr no longer aborts its runtime and no longer corrupts a frame.
• Lifecycle messages and connector frames share the channel and are dispatched by message type
  without starving each other, and permission replies keep their own admission budget.
• The child's stdin is no longer used for protocol traffic.
• The ported connector suites are registered in the repository's declared suite inventory and pass.
• A cancelled call still stops promptly, and a call in flight when the parent goes away settles
  rather than hanging.