F6: no declared instance Slug was ever checked against Slug's own grammar
before reaching Mind::require_instance's byte comparison, so a name outside
the grammar read as merely a foreign mind rather than being refused by its
own name.
Slug's grammar check is a crate-private trait in epiphany_pipeline, reachable
only through a real document, so require_grammatical_instance wraps the
declared name in a throwaway PipelineInstance and reads the answer back
through PipelineDocument::validate, the leaf's own public door; nothing here
re-derives the grammar. Daemon::handle asks it on the read path, before
Mind::require_instance, for every request that names an instance.
Add a_declared_instance_outside_the_grammar_is_refused_by_name_before_the_identity_check,
driving a fullwidth Latin small letter y, and mutation entry S3wide, which
folds a fullwidth character to plain ASCII before validating and dies
against it.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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