fix(docker): skip credential/skills/cache mounts when source is invalid (#24490) (#34331)

Salvages #24490 by @liuhao1024 against current main.

The Docker daemon will silently auto-create a directory at the host
path of any `-v <host>:<container>` bind mount when the host path
doesn't exist.  In Docker-in-Docker setups (where the outer host's
real credential file isn't visible inside the agent's parent
container), this leaves a directory at the credential mount source —
and the inner `docker run` then refuses to mount a directory over a
file destination with exit 125.

Add defensive shape guards to all three mount loops in
DockerEnvironment.__init__:

  * credentials (expected: file)  — skip + warn on directory or missing
  * skills      (expected: dir)   — skip + warn when not a directory
  * cache       (expected: dir)   — skip + warn when not a directory

Failed mounts surface as WARN logs rather than crashing the container
start.  Existing well-formed sources mount unchanged.

The original PR's branch was on a pre-container-reuse-rework base
(May 12) and conflicted with the post-May-28 driver work (label
tagging, container reuse, orphan reaper).  Reconstructed the same
intent on current main; the three guard blocks slot cleanly into
`tools/environments/docker.py` around the existing mount loops.

Three new tests pinned in `tests/tools/test_docker_environment.py`:
directory-source skip, missing-source skip, valid-file mounts.  Test-
first regression verification: reverted just the production code to
`origin/main` and confirmed the new tests fail with
`'deleted_token.json' is contained here: /root/.hermes/...` — the
fixed code makes them pass.  Full file passes (54/54).

Closes #24490

Co-authored-by: liuhao1024 <11816344+liuhao1024@users.noreply.github.com>

tools/environments/docker.py

@@ -12,6 +12,7 @@ import shutil
 import subprocess
 import sys
 import uuid
+from pathlib import Path
 from typing import Optional
 
 from tools.environments.base import BaseEnvironment, _popen_bash
@@ -577,6 +578,22 @@ class DockerEnvironment(BaseEnvironment):
             )
 
             for mount_entry in get_credential_file_mounts():
+                src = Path(mount_entry["host_path"])
+                if src.is_dir():
+                    # Docker-in-Docker: Docker auto-created the source path as
+                    # a directory when it didn't exist on the host.  Mounting a
+                    # directory over a file destination causes exit 125.
+                    logger.warning(
+                        "Docker: skipping credential mount — source is a directory "
+                        "(likely Docker-in-Docker auto-creation): %s",
+                        src,
+                    )
+                    continue
+                if not src.is_file():
+                    logger.warning(
+                        "Docker: skipping credential mount — source not found: %s", src,
+                    )
+                    continue
                 volume_args.extend([
                     "-v",
                     f"{mount_entry['host_path']}:{mount_entry['container_path']}:ro",
@@ -590,6 +607,13 @@ class DockerEnvironment(BaseEnvironment):
             # Mount skill directories (local + external) so skill
             # scripts/templates are available inside the container.
             for skills_mount in get_skills_directory_mount():
+                src = Path(skills_mount["host_path"])
+                if not src.is_dir():
+                    logger.warning(
+                        "Docker: skipping skills mount — source is not a directory: %s",
+                        src,
+                    )
+                    continue
                 volume_args.extend([
                     "-v",
                     f"{skills_mount['host_path']}:{skills_mount['container_path']}:ro",
@@ -605,6 +629,13 @@ class DockerEnvironment(BaseEnvironment):
             # cached media from inside the container.  Read-only — the
             # container reads these but the host gateway manages writes.
             for cache_mount in get_cache_directory_mounts():
+                src = Path(cache_mount["host_path"])
+                if not src.is_dir():
+                    logger.warning(
+                        "Docker: skipping cache mount — source is not a directory: %s",
+                        src,
+                    )
+                    continue
                 volume_args.extend([
                     "-v",
                     f"{cache_mount['host_path']}:{cache_mount['container_path']}:ro",