Fix UID/GID mismatch and SSH key permissions in container

- Entrypoint now runs as root to remap the container's claude user
  UID/GID to match the host user, fixing bind mount permission errors
  on WSL
- SSH keys are mounted read-only to a staging path (/tmp/.host-ssh)
  and copied to ~/.ssh with correct permissions by the entrypoint
- Exec sessions explicitly run as the claude user
- Host UID/GID detected automatically and passed as env vars

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

container/Dockerfile

@@ -88,7 +88,9 @@ RUN mkdir -p /home/claude/.claude /home/claude/.ssh
 
 WORKDIR /workspace
 
-COPY --chown=claude:claude entrypoint.sh /home/claude/entrypoint.sh
-RUN chmod +x /home/claude/entrypoint.sh
+# ── Switch back to root for entrypoint (handles UID/GID remapping) ─────────
+USER root
+COPY entrypoint.sh /usr/local/bin/entrypoint.sh
+RUN chmod +x /usr/local/bin/entrypoint.sh
 
-ENTRYPOINT ["/home/claude/entrypoint.sh"]
+ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]