Graph, schema, and append handlers share the daemon's guarded bearer/session authorization path and keep malformed TSV batches fully validated before storage mutation. Empty graph creation is permitted so HTTP graph lifecycle and schema registration can remain separate operations.

Constraint: use the existing graph-management permission because the built-in permission manifest is template-bound.
Rejected: extending the permission catalog in this change | it would require a template manifest migration outside the endpoint surface.
Confidence: high
Scope-risk: moderate
Directive: Keep tenant/path/query agreement checks before fact mutations and keep graph storage paths out of HTTP responses.
Tested: meson test -C builddir-issue50-fact --print-errorlogs; meson test -C builddir-issue50-default --print-errorlogs
Not-tested: JSONL and Arrow ingestion formats are intentionally deferred.
Co-authored-by: OmX <omx@oh-my-codex.dev>