feat(BREV-2866): open shell in expected container working directory

[nisolanki1209]

Problem

When launching a custom container, brev shell did not take the container’s WORKDIR into account. It opened a standard shell session, which defaults to the root user’s home directory, instead of the container’s WORKDIR.

As a result, users were placed in /root rather than the container’s intended WORKDIR.

Solution

Updated the runSSH function to detect and respect the container’s WORKDIR when launching brev shell.

• Detect the container WORKDIR by reading /proc/1/cwd (PID 1 working directory).
• Fallback to pwd if /proc/1/cwd is unavailable.
• Change into the resolved directory before starting the shell.
• Print a warning if the directory is not found, but still launch the shell to avoid blocking access to the container.
• Use ${SHELL} with /bin/sh as a fallback for minimal containers.

[Copilot]

Pull request overview

This PR updates the brev shell command to respect the container's WORKDIR when opening an interactive shell session in a custom container. Previously, users were placed in the default SSH login directory (/root) regardless of the container's intended working directory.

Changes:

• The runSSH function signature is updated to accept a host bool parameter, and the call site is updated accordingly.
• When host=false (the container path), the SSH command now reads /proc/1/cwd via readlink (with pwd as a fallback) to determine the container's working directory, then cds into it before executing the shell.
• The host=true path retains the original simple ssh command behavior without modifications.

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