Migrate remaining MAPL error macros

[tclune]

Parent

Builds on #5324 (named error catalog and macro foundation).

Goal

Migrate remaining MAPL-owned _ASSERT, _FAIL, and applicable _VERIFY sites to generated named error codes and context-aware macro forms.

Requirements

• Preserve existing numeric codes and return-code behavior.
• Classify every remaining site by semantic failure condition before assigning codes.
• Merge only semantically equivalent conditions; wording similarity alone is insufficient.
• Preserve useful site-specific context through _CTX values without duplicating diagnostic prose.
• Keep legacy macro behavior until each site is deliberately migrated.
• Maintain migration inventory and canonical-code review records.
• Run ctest -L ESSENTIAL with configured compiler stack.

Scope

MAPL-owned source only. External dependencies and unrelated feature work remain out of scope.

Follow-up

Link implementation PRs to this issue and parent #5324.