fix(vision): use HERMES_HOME-based cache dir instead of cwd (#17719)

vision_analyze used Path('./temp_vision_images') — a relative path that
resolved against cwd. Under Docker the image's WORKDIR is /opt/hermes,
which is root-owned and only chmoded a+rX (read + traversal). Since
#5811 landed (run as non-root hermes UID 10000, Apr 12), remote-URL
vision calls fail with PermissionError on mkdir.

Switch to get_hermes_dir('cache/vision', 'temp_vision_images'): resolves
to $HERMES_HOME/cache/vision/ (= /opt/data/cache/vision/ in Docker —
the user-owned volume mount). Existing installs with the old dir keep
using it via the get_hermes_dir back-compat path; no migration needed.

Only site in the codebase that stored runtime files via Path('./...').

Reported via Discord: https://juick.com/i/p/3089079.jpg → Telegram →
gateway → [Errno 13] Permission denied: 'temp_vision_images'.

tools/vision_tools.py

@@ -38,6 +38,7 @@ from typing import Any, Awaitable, Dict, Optional
 from urllib.parse import urlparse
 import httpx
 from agent.auxiliary_client import async_call_llm, extract_content_or_reasoning
+from hermes_constants import get_hermes_dir
 from tools.debug_helpers import DebugSession
 from tools.website_policy import check_website_access
 
@@ -435,7 +436,7 @@ async def vision_analyze_tool(
         Exception: If download fails, analysis fails, or API key is not set
         
     Note:
-        - For URLs, temporary images are stored in ./temp_vision_images/ and cleaned up
+        - For URLs, temporary images are stored under $HERMES_HOME/cache/vision/ and cleaned up
         - For local file paths, the file is used directly and NOT deleted
         - Supports common image formats (JPEG, PNG, GIF, WebP, etc.)
     """
@@ -483,7 +484,7 @@ async def vision_analyze_tool(
             if blocked:
                 raise PermissionError(blocked["message"])
             logger.info("Downloading image from URL...")
-            temp_dir = Path("./temp_vision_images")
+            temp_dir = get_hermes_dir("cache/vision", "temp_vision_images")
             temp_image_path = temp_dir / f"temp_image_{uuid.uuid4()}.jpg"
             await _download_image(image_url, temp_image_path)
             should_cleanup = True