fix: use runuser for privilege drop and capture container stderr in logs

The container still exited immediately after the su-based fix.  can
interfere with TTY/stdin handling for interactive shells. Switch to
, which is root-only, skips PAM, and preserves file descriptors so
bash stays interactive.

Also improve container failure diagnostics:
-  now combines stdout and stderr
- This helps surface the real reason when a container exits with code 0

Quality gates:
- pytest tests/unit: 219 passed
- ruff: clean on changed files
- mypy: clean on changed files

apps/api/src/services/docker/.pi-map.index.md

@@ -2,7 +2,7 @@
 dir: apps/api/src/services/docker
 
 ## role
-Provides Docker infrastructure services for container lifecycle management, compose orchestration, secure configuration deployment, and external tunnel exposure.
+Provides Docker infrastructure automation for container lifecycle management, service composition, secure configuration deployment, and external network tunneling.
 ## parent
 index: apps/api/src/services/.pi-map.index.md
 map: apps/api/src/services/.pi-map.md

apps/api/src/services/docker/.pi-map.md

@@ -4,15 +4,15 @@ dir: apps/api/src/services/docker
 index: apps/api/src/services/docker/.pi-map.index.md
 
 ## role
-Provides Docker infrastructure services for container lifecycle management, compose orchestration, secure configuration deployment, and external tunnel exposure.
+Provides Docker infrastructure automation for container lifecycle management, service composition, secure configuration deployment, and external network tunneling.
 ## files
 - __init__.py | Package initialization file that exposes Docker-related service functions for container operations, compose management, configuration staging, and tunnel management. | dep: src.services.docker.compose, src.services.docker.config_staging, src.services.docker.container, src.services.docker.tunnel
 - compose.py | Generates, renders, and executes Docker Compose files with volume sorting and template variable substitution. | exp: func:sort_volumes_by_specificity(volumes: list[str]) → list[str], call:vol.split, call:len, call:parts[1].rstrip, call:target.count, call:targets.append, call:Counter(targets).items, call:logger.warning, call:sorted, func:_target_depth(vol: str) → int, call:vol.split, call:len, call:parts[1].rstrip, call:target.count, func:render_compose_template(template: str, variables: dict[str, Any]) → str, call:variables.items, call:result.replace, call:str, call:aliases.items, call:variables.get, func:write_compose_file(instance_dir: str, content: str) → str, call:Path, call:compose_path.write_text, call:str, func:execute_compose_command(compose_path: str, action: str, timeout, env_file) → tuple[int, str, str], call:Path, call:cmd.extend, call:cmd.append, call:subprocess.run, call:str, raise:ValueError | dep: logging, subprocess, collections, pathlib, typing, collections.Counter, pathlib.Path, typing.Any
 - config_staging.py | Stages configuration files into instance directories with security checks for path traversal. | exp: func:ensure_instance_directory(instance_id: str, base_path) → str, call:Settings, call:Path, call:instance_dir.mkdir, call:str, call:instance_dir.absolute, func:write_env_file(instance_dir: str, env_vars: dict[str, str]) → str, call:Path, call:env_vars.items, call:env_path.write_text, call:"\n".join, call:str, func:write_config_files(instance_dir: str, files: dict[str, str]) → None, call:Path, call:files.items, call:full_path.resolve().relative_to, call:instance_path.resolve, call:full_path.parent.mkdir, call:full_path.write_text, raise:ValueError | dep: logging, pathlib, src.config, src.config.Settings
-- container.py | Provides Docker container runtime queries and network management utilities via subprocess calls to the Docker CLI. | exp: func:get_container_id(instance_name: str) → str | None, call:instance_name.lower, call:subprocess.run, call:result.stdout.strip, call:ps_result.stdout.strip().splitlines, call:line.split, call:len, call:name.lower, func:get_container_name(instance_name: str) → str | None, call:subprocess.run, call:instance_name.lower, call:result.stdout.strip().lstrip, func:get_backend_network_name() → str, call:subprocess.run, call:result.stdout.strip().split, call:net.lower, func:connect_container_to_network(container_name: str, network_name) → bool, call:get_backend_network_name, call:subprocess.run, func:get_container_ip_on_network(container_id: str, network_name) → str | None, call:get_backend_network_name, call:subprocess.run, call:result.stdout.strip, func:is_container_on_network(container_id: str, network_name) → bool, call:get_backend_network_name, call:subprocess.run, func:get_container_status(container_id: str) → dict[str, Any], call:subprocess.run, call:result.stdout.strip().split, call:int, call:len, call:parts[1].isdigit, func:wait_for_container_running(container_id: str, timeout, interval) → dict[str, Any], call:time.time, call:get_container_status, call:time.sleep, func:get_container_logs(container_id: str, tail) → str, call:subprocess.run, call:str, func:find_free_port(start, end) → int, call:range, call:socket.socket, call:s.connect_ex, raise:RuntimeError | dep: logging, subprocess, time, typing, socket
+- container.py | Provides utility functions for querying Docker container runtime state, managing container network connections, and finding free TCP ports via subprocess calls to the Docker CLI. | exp: func:get_container_id(instance_name: str) → str | None, call:instance_name.lower, call:subprocess.run, call:result.stdout.strip, call:ps_result.stdout.strip().splitlines, call:line.split, call:len, call:name.lower, func:get_container_name(instance_name: str) → str | None, call:subprocess.run, call:instance_name.lower, call:result.stdout.strip().lstrip, func:get_backend_network_name() → str, call:subprocess.run, call:result.stdout.strip().split, call:net.lower, func:connect_container_to_network(container_name: str, network_name) → bool, call:get_backend_network_name, call:subprocess.run, func:get_container_ip_on_network(container_id: str, network_name) → str | None, call:get_backend_network_name, call:subprocess.run, call:result.stdout.strip, func:is_container_on_network(container_id: str, network_name) → bool, call:get_backend_network_name, call:subprocess.run, func:get_container_status(container_id: str) → dict[str, Any], call:subprocess.run, call:result.stdout.strip().split, call:int, call:len, call:parts[1].isdigit, func:wait_for_container_running(container_id: str, timeout, interval) → dict[str, Any], call:time.time, call:get_container_status, call:time.sleep, func:get_container_logs(container_id: str, tail) → str, call:subprocess.run, call:str, func:find_free_port(start, end) → int, call:range, call:socket.socket, call:s.connect_ex, raise:RuntimeError | dep: logging, subprocess, time, typing, socket
 - tunnel.py | Manages Cloudflare tunnels by orchestrating cloudflared Docker containers to expose internal services via temporary public URLs. | exp: func:_tunnel_container_name(instance_name: str) → str, call:instance_name.lower, func:_ensure_image() → None, call:subprocess.run, call:result.stdout.strip, call:logger.info, call:logger.warning, func:_cleanup_stale_tunnel(tunnel_name: str) → None, call:subprocess.run, func:_get_tunnel_logs(tunnel_name: str) → tuple[str, str], call:subprocess.run, func:_get_tunnel_exit_code(tunnel_name: str) → int | None, call:subprocess.run, call:int, call:result.stdout.strip, func:start_tunnel(instance_name: str, container_port: int, timeout, target_url) → dict[str, str], call:_ensure_image, call:_tunnel_container_name, call:_cleanup_stale_tunnel, call:instance_name.lower, call:get_backend_network_name, call:logger.debug, call:" ".join, call:subprocess.run, call:proc.stdout.strip, call:re.compile, call:__import__("time").time, call:_get_tunnel_logs, call:url_pattern.search, call:match.group, call:_get_tunnel_exit_code, call:__import__("time").sleep, call:logger.info, raise:RuntimeError, func:stop_tunnel(instance_name: str) → None, call:_tunnel_container_name, call:_cleanup_stale_tunnel, call:logger.debug, func:recreate_tunnel(instance_name: str, container_port: int, target_url) → dict[str, str], call:stop_tunnel, call:start_tunnel, func:check_tunnel_health(url: str, timeout) → dict[str, Any], call:subprocess.run, call:int, call:result.stdout.strip, call:str(exc).lower, call:any | dep: logging, re, subprocess, typing, src.services.docker.container
 ## arch
-Service-oriented utility modules with subprocess-based Docker CLI integration, Jinja2 templating for compose generation, and security-hardened file operations with path traversal validation.
+Subprocess-based CLI wrapper architecture with template-driven file generation, security-validated file staging, and container-orchestrated tunnel proxying.
 ## tags
 tunnel, container, call:subprocess.run, get, name, call:, network, call:result.stdout.strip
 ## symbols

apps/api/src/services/docker/container.py

@@ -283,7 +283,7 @@ def get_container_logs(container_id: str, tail: int = 100) -> str:
         tail: Number of lines to return
 
     Returns:
-        Container logs
+        Container logs (stdout + stderr)
     """
     result = subprocess.run(
         ["docker", "logs", "--tail", str(tail), container_id],
@@ -291,9 +291,15 @@ def get_container_logs(container_id: str, tail: int = 100) -> str:
         text=True,
     )
 
-    if result.returncode == 0:
-        return result.stdout
-    return f"Failed to get logs: {result.stderr}"
+    if result.returncode != 0:
+        return f"Failed to get logs: {result.stderr}"
+
+    logs = result.stdout
+    if result.stderr:
+        if logs:
+            logs += "\n"
+        logs += f"STDERR:\n{result.stderr}"
+    return logs
 
 
 def find_free_port(start: int = 10000, end: int = 20000) -> int: