Feat/cs/arch fixes

[ReagentX]

• Move the daemon handshake to a dedicated v3 hello frame, with compact lossless base64 environment encoding.
• Carry each client’s launch environment and working directory through the handshake, so daemon-spawned tasks use the correct client context.
• Reject launches without a launch context rather than falling back to daemon process state.
• Improve reconnect handling when the daemon is busy, including bounded handshake writes.
• Preserve process-group teardown semantics for removed tasks during shutdown and consistently report signal-based exit codes.
• Expand protocol, daemon, supervisor, and task coverage for the new handshake and teardown behavior.