nightly: Select ACP v2 for beta connections (#65892)
- Select ACP v2 for new connections when the existing
acp-betafeature
flag is enabled; leave flag-off connections on v1 and preserve v1 beta
behavior on fallback. - Start a fresh v1 process/transport only after a correlated
initialization exchange establishes v1-only support: a valid v1
initialization response or structured-32022data withrequested: 2
and a well-formedsupportedlist containing 1 but not 2. Do not guess
from error-message text or retry malformed initialization, unrelated
protocol errors, or ordinary transport failures. - Drain initialization output on natural process exit before classifying
failure, preserving structured negotiation diagnostics even when the
agent exits immediately after rejection. - Include v2 connections in the existing ACP logs UI without adding
debug-log requirements to the generic connection trait.
This is behavior-changing activation for the existing acp-beta
audience.
Release Notes:
- N/A