fix(scip): route SymbolInformation.kind by the SCIP schema numbers - #1742

Summary

ScipIndexParser routed definitions with kind 18 as Enum, 20 as Interface and 54 as Protocol. In scip.proto
those numbers are Getter, Instance and Type; Enum is 11, Interface 21 and Protocol 42. Producers that report
real kinds therefore lost their interfaces, enums and protocols, and a getter was filed as an enum. For example,
scip-go reports type Reader interface as kind 21, and CGC dropped it.

The kinds CGC infers for producers that report 0 used the same old numbers (C/C++ enum 18, an interface detected from
source 20). They move to the schema values too, so routing has a single numbering for real and inferred kinds. Keeping
18 as an Enum alias was not an option, because a real 18 is a Getter.

The routed kinds now come from scip_pb2.SymbolInformation (Enum, Interface, Protocol) instead of literals.
scip_indexer.py: +10 / −6. No new node types: kinds without a representation (Getter, Instance, Type, …) are still not
materialized; they are just no longer mistaken for Enum / Interface / Protocol.

Tests

• tests/unit/tools/test_scip_modern_kinds.py (new): kinds 11 / 21 / 42 reach enums / interfaces; Getter 18 is
  not an enum, Instance 20 and Type 54 are not interfaces; class / struct / trait / function / method / field / variable
  unchanged; kind-0 fallbacks (source interface, C++ enum) still land in interfaces / enums. 7 of these cases fail
  on main.
• tests/unit/tools/test_scip_indexer_c_family.py: _infer_cxx_zero_kind now returns 11 for C/C++ enums.
• Real producer: scip-go (scip-code/scip-go@28f28d8) on a small Go package. Reported kinds: Reader 21, Item 49,
  Name 15, Make 17, Item.Read 26. On main the parser drops Reader; with this change it is an interface, and
  every other node is unchanged.
• ./tests/run_tests.sh fast (Python 3.12): 1623 passed, 8 skipped, 0 failed (main: 1608 passed, 8 skipped,
  0 failed; the difference is the new tests).
• The change also applies cleanly on top of fix(scip): recognise scip-dotnet (+N) overloads and drop the marker from names #1740, and the SCIP tests pass with both.

Not in scope

Discovered separately: scip-go writes only the typed Occurrence range fields, which the bundled scip_pb2 does not
know yet; that is a separate change.

🤖 Generated with Claude Code