[TASK][CORE-01.T04] Build bounded wire framing and errors

Parent: #2

Task ID: `CORE-01.T04`

## Proposed implementation
Add request/response/event envelopes, length-prefix decoding, request correlation, deadline propagation and stable error codes. Validate lengths before allocation, cap nesting/collections and reserve a control lane separate from large artifacts.

## Done when
Fragmented, oversized, malformed and deeply nested payload fixtures remain memory-bounded and return stable errors.

## Guardrail
Never parse a partially received action as executable.

## Prerequisites
`CORE-01.T03`

Review: pending · Implementation: not started.

Start by reviewing prerequisite CORE-01.T03 and tracing the current wire-message handling. Use fragmented, oversized, malformed, and deeply nested payload fixtures as the completion checks: inputs remain memory-bounded, return stable errors, and never execute a partially received action.

Written by the indexing model from the issue text.