When OPENCLAW_HOME is set (indicating an isolated instance), the gateway
port should be read from config rather than inheriting OPENCLAW_GATEWAY_PORT
from a parent process. This fixes running multiple OpenClaw instances
where a child process would incorrectly use the parent's port.
Changes:
- resolveGatewayPort() now prioritizes config.gateway.port when OPENCLAW_HOME is set
- Added getConfigPath() function for runtime-evaluated config path
- Deprecated CONFIG_PATH constant with warning about module-load-time evaluation
- Updated gateway run command to use getConfigPath() instead of CONFIG_PATH
Fixes the issue where spawning a sandbox OpenClaw instance from within
another OpenClaw process would fail because OPENCLAW_GATEWAY_PORT from
the parent (set in server.impl.ts) would override the child's config.
