Phase 0 of any_type_componentization_20260621. Adds the canonical
decision rule that future contributors can apply without re-deriving:
- TypeAlias conditions: open shape, self-describing, transient
- dataclass(frozen=True) conditions: known fields, multi-site access,
stable serialization, shared across modules
- The src/vendor_capabilities.py reference pattern (5 properties)
- Decision tree
- The 5 worked examples (89 sites promoted per the audit)
- Cross-references to audit scripts + input artifact + track
This is the canonical artifact for the 'when to dataclass' question;
subsequent phases refer to it via 'see styleguide 12' rather than
re-deriving the rule.
ed
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