chore: clone opstool for visualization reference

opstool v1.0.26 (GPL-3.0) is cloned read-only under
.slim/clonedeps/repos/ to inspect its PyVista/Plotly visualization
settings. GPLv3 section 13 permits combining it with this AGPL-3.0
project. The clone itself is git-ignored; the manifest and the AGENTS.md
pointer are committed.

AGENTS.md

@@ -57,3 +57,17 @@ git remote add origin ssh://git@smill-home.ddns.net/smill/otko.git
 - `examples/*.py` are source of truth; `examples/*.osmodel` are generated artifacts (checked in). Never hand-edit `.osmodel` — change the script and regen: `python examples/cantilever.py` (each script saves, reloads, asserts clean round-trip).
 - Projects persist as single Pydantic-validated JSON `.osmodel` (diffable); analysis output goes to `*.osresults.h5` (HDF5, one group per case).
 - Quick smoke: open `examples/cantilever.osmodel` → run `Tip-Load` → M3 peaks 50 kN·m at fixed end.
+
+## Cloned Dependency Source
+
+Read-only dependency source repositories are available under
+`.slim/clonedeps/repos/` for inspection. Do not edit these clones. The
+structured manifest is `.slim/clonedeps.json`.
+
+- `.slim/clonedeps/repos/yexiang92__opstool/` — `yexiang92/opstool` at `v1.0.26`; the OpenSeesPy
+  pre/post-processor whose PyVista and Plotly visualization settings
+  (`opstool/vis/{pyvista,plotly}/plot_utils.py`, `plot_resp_base.py`, `vis_model.py`) are the
+  reference for otko's canvas look-and-feel. GPL-3.0, and GPLv3 §13 explicitly permits combining
+  it with otko's AGPL-3.0. Any code actually ported from it must keep the opstool copyright notice
+  and record that it was modified (GPLv3 §5a/b) — add that entry to `NOTICE` when the port lands.
+