~anthropic/claude-sonnet-latest → B (6:4)

B fixes a real correctness bug (root/tilde canonicalization mismatch causing top-level ontology children to be mis-keyed), adds targeted unit/integration/browser tests validating the fix, and introduces a clear invariant (SLUG_TILDE_ONTOLOGY_ROOT normalization) reused across modules. A is a substantial refactor moving fetch logic into a new SSE-based module with real functional improvement (async streaming, job-completion notification) but is mostly architectural churn/rename plus feature addition rather than a bugfix, and removes some existing test coverage without clearly stronger regression guarantees than B's added tests.