copilot-sdk harness drops proxy variables, so the Planner can't run behind a proxy #759

When Chopin runs behind an HTTPS proxy, the Planner fails with "The Planner stream failed. Try again." The server logs:

Request session.create failed with message: network fetch failed: request failed:
error sending request for url (https://api.github.com/copilot_internal/user)

defaultConnect in apps/server/src/harness/copilot-sdk/adapter.ts creates the client with
env: { COPILOT_PLUGIN_DIR_ONLY: "true" }. The SDK uses that as the CLI's whole environment, so
HTTPS_PROXY, HTTP_PROXY and NO_PROXY never reach the CLI. The server process itself uses the
proxy, so sign-in and the GitHub tools work; only the CLI goes direct.

Suggested fix: pass the proxy variables through, for example

env: { ...pick(process.env, ["HTTPS_PROXY", "HTTP_PROXY", "NO_PROXY", "https_proxy", "http_proxy", "no_proxy"]), COPILOT_PLUGIN_DIR_ONLY: "true" }

Same for any other place that creates a CopilotClient with env.

Seen at e47b1a5. We work around it by pointing COPILOT_CLI_PATH at a
script that sets the proxy and execs the bundled CLI.