fix: HERMES_WEBUI_DEFAULT_WORKSPACE wins over settings.json; trust DEFAULT_WORKSPACE subtree (#610)

Squash-merges PR #610. Fixes Docker workspace env var override and trust validation (issue #609). 1367 tests passing, QA harness green. Reviewed by independent agent (see PR comments).

api/workspace.py

@@ -283,9 +283,22 @@ def resolve_trusted_workspace(path: str | Path | None = None) -> Path:
     except Exception:
         pass
 
+    # (C) Trusted if it is equal to or under the boot-time DEFAULT_WORKSPACE.
+    #     In Docker deployments HERMES_WEBUI_DEFAULT_WORKSPACE is often set to a
+    #     volume mount outside the user's home (e.g. /data/workspace).  That path
+    #     was already validated at server startup, so any sub-path of it is safe
+    #     without requiring the user to add it to the workspace list manually.
+    try:
+        boot_default = Path(_BOOT_DEFAULT_WORKSPACE).expanduser().resolve()
+        candidate.relative_to(boot_default)
+        return candidate
+    except ValueError:
+        pass
+
     raise ValueError(
-        f"Path is outside the user home directory and not in the saved workspace "
-        f"list: {candidate}. Add it via Settings → Workspaces first."
+        f"Path is outside the user home directory, not in the saved workspace "
+        f"list, and not under the default workspace: {candidate}. "
+        f"Add it via Settings → Workspaces first."
     )