…VIDIA#2242)

* toolshed: handle anonymous struct renames in check_cython_abi.py

The name of an anonymous struct is an implementation detail, so it is
acceptable for the name to change between builds (e.g. from the old
anon_structXX / anon_unionXX scheme to the newer MODULE__anon_podXX
scheme that Cython now emits).  This change makes the checker verify
that anonymous structs have the same *structure*, while tolerating name
changes, so spurious "Missing" / "Added" errors are no longer reported
for pure renames.

Three improvements:

1. `_format_base_type_name`: unwrap `CConstOrVolatileTypeNode` instead
   of falling through to its class name.  Const/volatile qualifiers do
   not affect ABI layout, and the old behaviour stored the Python class
   name literally ("CConstOrVolatileTypeNode*") in generated .abi.json
   files, which caused field-type mismatches when comparing builds where
   the qualifier was expressed differently.

2. `_build_anon_rename_map`: new iterative bottom-up pass that builds a
   mapping from old-style anon names (expected) to new-style anon_pod
   names (found) by matching field content.  Leaf structs (no anon-type
   fields) are matched first; each round normalises the remaining
   candidates using already-known renames, allowing parent structs that
   embed renamed children to match in subsequent rounds.

3. `_normalize_type`: uses `re.sub` with `\b` word-boundary anchors
   instead of plain `str.replace`, so a shorter name like "anon_struct1"
   cannot corrupt a longer one like "anon_struct12" if iteration order
   happens to process the shorter key first.

`check_structs` is updated to look up each expected struct through the
rename map, normalise expected field types before comparing, and skip
the "Added" report for new-style names that are confirmed renames.

Note: baselines generated with the old tool (containing
"CConstOrVolatileTypeNode*" type strings) must be regenerated with the
fixed tool before the rename-matching logic can work correctly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Ignore private parts of the ABI

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Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>