Revert PR #367 blob read surface

[aaltshuler]

Summary

• revert the complete 12-commit PR Replace read_blob with descriptor-first read_blob_at facade #367 range (8cbf8669^..55d3d214) as one feature unit
• remove the descriptor-first blob read facade, HTTP GET/HEAD /blob endpoint, CLI blob get/stat commands, wire/OpenAPI surface, validators, dependencies, tests, and user documentation introduced by that PR
• restore the pre-Replace read_blob with descriptor-first read_blob_at facade #367 public contract while preserving the later RFC-026 private MemWAL B1 implementation from Implement RFC-026 private MemWAL B1 core #371

Why

PR #367 introduced a major public engine, HTTP, and CLI feature without the RFC governance agreement required for changes of this scope. Keeping selected pieces would preserve an architecture and contract that were never approved. This exact revert restores the governance boundary; any successor blob-delivery design should return through the RFC process before implementation.

Impact

The public blob download/stat feature added by #367 is removed. Existing pre-#367 blob behavior remains, including Omnigraph::read_blob and external-URI materialization. RFC-026 B1 also remains intact; its URI-backed blob materialization concern is separate and is not attributed to #367.

Validation

• cargo test --workspace --locked
• cargo test -p omnigraph-engine --features failpoints --test memwal_stream --locked (24/24)
• cargo test -p omnigraph-engine --test forbidden_apis --test lance_surface_guards --locked (40/40)
• cargo test -p omnigraph-server --test openapi --locked (84/84)
• focused pre-Replace read_blob with descriptor-first read_blob_at facade #367 blob behavior suites
• scripts/check-agents-md.sh
• cargo metadata --locked --no-deps
• git diff --check

Greptile Summary

This PR restores the blob behavior that existed before PR #367. The main changes are:

• Removes the HTTP and CLI blob read surfaces.
• Restores the older Omnigraph::read_blob API.
• Removes descriptor types, validators, dependencies, tests, and documentation.
• Updates the generated OpenAPI contract.

Confidence Score: 4/5

Blob-bearing create and overwrite operations can commit invalid persistent state, so these paths need fixes before merging.

• Noncanonical blob schemas can break later keyed writes.
• Unreadable external references can become durable and fail during later reads or rewrites.
• The CLI, server, API-type, and OpenAPI removals are otherwise coordinated.

crates/omnigraph/src/table_store.rs

Important Files Changed

Filename	Overview
crates/omnigraph/src/table_store.rs	Removes blob validation from durable create and overwrite paths, allowing incompatible schemas and unreadable external references to be committed.
crates/omnigraph/src/db/omnigraph.rs	Restores the older read_blob method using Lance BlobFile.
crates/omnigraph-server/src/lib.rs	Removes the protected blob route and its related imports.
crates/omnigraph-cli/src/client.rs	Removes remote and embedded blob get/stat operations.
crates/omnigraph-api-types/src/lib.rs	Removes the blob query DTO and ETag helper.
openapi.json	Removes the blob endpoint from the public API contract.

_{Reviews (1): Last reviewed commit: "Revert PR #367 blob read surface" | Re-trigger Greptile}

Greptile also left 2 inline comments on this PR.

Context used:

• Context used - AGENTS.md (source)
• Context used - CLAUDE.md (source)