fix(air): canonicalize type identities

[akonwi]

Summary

• canonicalize structural AIR types through one child-TypeID-based interner
• require checker-resolved executable expression types and reserve Void exclusively for Ard's unit type
• canonicalize nominal declarations, generic applications, foreign named types, and owner-scoped type parameters
• add explicit nominal reservation/completion/failure lifecycle handling
• harden AIR validation for duplicate identities, generic relationships, foreign metadata, and generic call type arguments
• document and accept ADR 0070

Details

This fixes the split identity domain between checker-derived and lowering-synthesized types that allowed one semantic Result<Void, Error> to receive multiple AIR TypeIDs. Constructor validation remains strict; the producer now guarantees canonical identity instead of compensating with structural assignability.

The checker-to-AIR boundary now preserves checked executable types, models non-returning expressions with a checker-only Never type, and rejects unresolved call inference variables. Recursive nominal types use explicit lowerer-owned lifecycle state so incomplete metadata cannot escape finalized AIR.

Testing

• cd compiler && go test -p 1 ./... -count=1
• sibling regression checks/builds for tinear, akonwi.github.io, dram, kb, maestro, and migrate
• sibling test suites for ard-cloudflare, cooper, decode, and ard-sql: 296 tests passed

Fixes #466

[vercel]

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Project	Deployment	Actions	Updated
ard-lang-dev	Ready	Preview	Sep 8, 2026 3:24pm UTC