Headless, API-first, agent-optimized native engine = canonical-mode shard backend.
Thesis: a page-store kernel with a typed-extension runtime; everything beyond the
c2-minimum is a typed extension activated per shard, and the shard's §A capability
profile is DERIVED from its active extensions (configuration->capability->conformance).
9 engine invariants (engine-is-one-shard, small kernel, per-shard activation,
profile-from-extensions, headless/agent-first, reuse-not-reinvent, typed+verified).
Kernel (4 concepts), typed-extension model (typed hooks + deterministic composition +
feature-control activation), T2 featureset/conflict-mediation realized, engine-as-shard,
agent-first API surface, module sketch, reuse (consumes feature-control/authorization;
G1 framework proposal), traceability, decisions/open, stability note. Marks T5 done.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
