feat(core): add language-neutral typed frontend contracts

[fffonion]

Summary

• Introduce language-neutral host catalog, module type/value identity and linked checked-source contracts for external frontends.
• Share strict typing, source-owned ownership admission and finalized logical schemas across compile, analysis, type hints, semantic models and executable callable prototypes.
• Keep type-only source admission separate from runtime reachability and host/callable authority.
• Retire Core frontend-specific compatibility paths; TypeScript parsing and language policy remain in the separate compat frontend repository.

Verification

• Exact candidate: 310a506d51f29d70f292a2f734b38e586b8bea3c.
• All 30 applicable clean final-HEAD gates passed, after the complete 30-gate corrected-source matrix.
• 453 unique target/test identities: 445 meaningful cases and 8 separately tracked helpers. All prior 444 obligations retained; 9 added.
• 52 maintained frontend cases; 4 real native response-JSON cases executed in both feature modes.
• Native/package checks and response-JSON tests are recorded; no wasm32 target or guest-ABI execution claim.
• Independent whole-Core review plus scoped R01–R04/direct-regression review: zero remaining blockers. Existing static-cost note Q01 is nonblocking and retained.

Scope

Core-only PR against master; the companion compat frontend will pin this exact published revision and be delivered separately.