feat(mcp): harden remote assets and job execution

Gate source-file downloads and verify registry paths and content hashes. Stream multipart uploads with bounded limits, supervise OpenCode jobs with explicit result markers and timeouts, and preserve managed endpoint security settings. Document the trusted-client boundary and add focused regression coverage.

Validation: PYTHONPATH=<staged-tree> python -m unittest discover -s tests (182 tests)

pyproject.toml

@@ -34,7 +34,10 @@ classifiers = [
 dependencies = []
 
 [project.optional-dependencies]
-mcp = ["mcp[cli]>=1.28,<2; python_version >= '3.10'"]
+mcp = [
+  "mcp[cli]>=1.28,<2; python_version >= '3.10'",
+  "python-multipart>=0.0.20,<1; python_version >= '3.10'",
+]
 
 [project.urls]
 Homepage = "https://github.com/Ar9av/obsidian-wiki"