bug: removing the proxy env makes AWS SDK Bedrock clients use h2-only, which the L7 proxy refuses #3709

User Story

As a user who runs OpenClaw with Amazon Bedrock in an OpenShell sandbox,
I want the agent's Bedrock chat requests to go through the sandbox's HTTP/1.1 L7 mediation,
so that the agent can call the model while the policy still inspects the traffic and injects credentials.

Problem Statement

Since #2942 (c1f2e71), the boundary removes the proxy variables (PROXY_ENV_VARS in crates/openshell-sandbox/src/process.rs) from every child process and from each exec. Before #2942, child_env.rs set HTTP_PROXY/HTTPS_PROXY=http://10.200.0.1:3128, NO_PROXY=127.0.0.1,localhost,::1 and NODE_USE_ENV_PROXY=1.

The OpenClaw Bedrock plugin (@openclaw/amazon-bedrock-provider@2026.8.2) selects its HTTP handler from these variables:

• If a proxy variable is set, the chat client uses NodeHttpHandler with a proxy agent (HTTP/1.1 through CONNECT).
• If no proxy variable is set, it uses the default of @aws-sdk/client-bedrock-runtime, which is NodeHttp2Handler. That handler offers only h2 in ALPN.

The L7 proxy offers only http/1.1 (l7/tls.rs). With no common protocol, the TLS handshake fails with alert 120 (RFC 7301 §3.2).

Related: #2426 (h2 ALPN in the L7 proxy), #3377 (another env regression from #2942, also found with OpenClaw).

Impact / Why This Matters

OpenClaw chat requests to Bedrock fail, so the agent cannot use Bedrock models.

Workarounds:

• AWS_BEDROCK_FORCE_HTTP1=1 makes the chat client use HTTP/1.1. It is an OpenClaw switch, not an AWS SDK switch.
• tls: skip for the Bedrock endpoint lets the h2 handshake complete, but it turns off L7 inspection and credential injection.

Other clients that select HTTP/1.1 only when a proxy variable is set probably have the same problem.

Acceptance Criteria

• An OpenClaw Bedrock chat request through L7 mediation completes without AWS_BEDROCK_FORCE_HTTP1.
• A client that reads the proxy variables to select its protocol gets the same behavior that it had before feat(isolation): implement the RFC 0012 sandbox architecture #2942, or the docs list the change and a workaround.

Reproduction Steps

1. Create a sandbox from an OpenClaw image, and install @openclaw/amazon-bedrock-provider@2026.8.2.
2. Give it a policy that sends TLS to bedrock-runtime.<region>.amazonaws.com through the L7 proxy, and a Bedrock credential.
3. Start the OpenClaw gateway, and send a chat message.
4. The request fails with the error in Logs.
5. Set AWS_BEDROCK_FORCE_HTTP1=1, and do step 3 again. The request completes.

Environment

• OpenShell: isolation crates at 24706c1 (main, after feat(isolation): implement the RFC 0012 sandbox architecture #2942)
• Runtime: k3s on colima (macOS)