Add named error code catalog and diagnostics

[tclune]

Summary

Introduce stable named error codes across MAPL error handling, backed by a versioned YAML catalog read through ESMF HConfig.

Scope

• Add hardwired diagnostics for missing, malformed/partial, and _VERIFY failures.
• Preserve stack/status context and standard-output reporting in serial and MPI paths.
• Add code-bearing _ASSERT_CODE and _FAIL_CODE forms while preserving legacy macro forms.
• Cover existing MAPL codes and staged migration of representative macro sites.
• Group semantically equivalent errors through maintainer-reviewed merge decisions; wording similarity alone is insufficient.

Acceptance Criteria

• Catalog validation rejects duplicate, missing, malformed, partial, unsupported-version, and undefined-code cases without replacing valid mappings.
• Same-path initialization is idempotent; invalid or different-path replacement preserves active mappings.
• Migrated assertion/failure sites use canonical codes and retain useful context.
• _VERIFY uses hardwired propagation diagnostics.
• Tests cover catalog, fallback, macro, stdout, and semantic-merge requirements.

Design Artifacts

• specs/001-named-error-codes/spec.md
• specs/001-named-error-codes/plan.md
• specs/001-named-error-codes/tasks.md

Implementation must link this issue before source modification, per MAPL constitution.