Fix inherited simpleContent scalar types and runtime text slots

[nth-bailey]

Derived simpleContent fields were typed as their complex base model rather than its inherited scalar, so valid numeric/string text failed generated Python construction and native record lookup returned an empty inherited slot. Resolve text references after import/include merging, retain named scalar constraints and complex bases, reject textual inheritance cycles, and keep one most-derived runtime text slot. TypeScript now inherits objects only from complex bases.

Stacked on #143. Tested source: 4421e3ce9f76024121919cc3d2f7fa5a1ecced24; later changes retain documentation/evidence only. Main is unchanged.

Validation:

• Full gate: 340 Rust tests, 115 Python tests, 100% statement/branch wrapper coverage; fmt, strict workspace Clippy and Ruff clean.
• Five core regressions plus compiled/executed consumers in all seven languages. Rust owned/borrowed XML + Serde, Python dataclass/Pydantic, Go and C# record/class XML/JSON round trips. Strict C++ and TypeScript compilation. The older Java decimal consumer now verifies scalar text directly.
• Independent libxml2 validation: three valid fixtures accepted and three invalid scalar/facet fixtures rejected; all-seven CLI emission smoke passes.
• Fresh matching CLI/native probes pass. Bounded W3C CType improves 23/28 → 26/28 round trips, removing all three targeted failures; schemas remain 31/31. AttrDecl remains 50/50 and NIST 447/452.

C# net8.0 consumers execute on .NET 10 with major roll-forward, not the minimum .NET 8 runtime. This does not implement extra facets inside simpleContent restrictions, empty/list text codecs, optional C# scalar attribute proxies, or full W3C conformance. The remaining two CType substitution-root failures and one NIST scalar group remain separate.

Report: research/runtime-simple-content-2026-10-03.md; raw logs, artifact hashes, toolchain versions, replay scripts and SHA256SUMS are retained under research/data/runtime-followups-2026-10-03/simple-content/. No additional performance claim is made for this schema fix.