[plenarius]

Found while scanning the Layonara haks' 27,000 tile models (see layonara/nwn-haks#23).

• NaN warnings: NaN/Inf floats in a binary are reported once per list of a node. The warning names the node and the list (verts, tangents, a controller, ...) and gives the count; before, there was one line per float with neither. One damaged tin01 tile went from 218 lines to 3.
• ASCII list warnings name the node and the list as well as the line: line 130: node "Mesh248", verts: "2>4000001" is read as 2, ....
• Light controller 144 (written by older EE compilers, nwn-mdl-spec E51) is dropped with an info note in the new Model.Notes / "notes" JSON field, not an unknown-controller warning. It made 2,019 lights in the haks look damaged. Notes are not counted as warnings, and the text output shows them only with --verbose.
• Unknown-controller warnings give the byte offset of the controller key; before, the offset field held the controller type.
• lightmapped_tile is removed. The byte it reads is uninitialised in the game's output, and the game reads no ASCII keyword for it (nwn-mdl-spec MDL-BIN-051).

Ported to python/ (decompiler and parser). DESIGN.md documents the warnings, parse_warnings and notes fields.

Testing:

• go test ./... passes, plus three new tests in pkg/mdl/decompile_where_test.go.
• parity_test.py, parity_parse.py and parity_compile.py pass.
• Go and Python give identical warnings and notes on 1,247 binary tile models and fixtures.
• Compiled output is unchanged: no compiler code was touched.

Follow-ups, not in this PR:

• cleanmodels-qt does not show notes yet.
• The writer still emits lightmapped N from the uninitialised byte.