Revert "Add pre-commit hook for openapi.json drift"

This reverts commit 7c6d89d194.

.pre-commit-config.yaml

@@ -1,10 +0,0 @@
-repos:
-  - repo: local
-    hooks:
-      - id: openapi-sync
-        name: Sync openapi.json
-        description: Regenerate openapi.json when the server API surface changes.
-        entry: bash -c 'OMNIGRAPH_UPDATE_OPENAPI=1 cargo test -p omnigraph-server --test openapi openapi_spec_is_up_to_date --quiet'
-        language: system
-        pass_filenames: false
-        files: ^(crates/omnigraph-server/src/.*\.rs|crates/omnigraph-server/Cargo\.toml|openapi\.json)$

CONTRIBUTING.md

@@ -16,24 +16,6 @@ cargo test --workspace
 If you touch S3-backed flows, the CI model uses a local RustFS instance for
 integration tests.
 
-### OpenAPI spec
-
-`openapi.json` is a committed artifact generated from the Utoipa annotations in
-`crates/omnigraph-server`. CI fails if it drifts from the source. To regenerate
-manually:
-
-```bash
-OMNIGRAPH_UPDATE_OPENAPI=1 cargo test -p omnigraph-server --test openapi openapi_spec_is_up_to_date
-```
-
-Optional: install [pre-commit](https://pre-commit.com) to run this automatically
-before each commit that touches the server:
-
-```bash
-pip install pre-commit
-pre-commit install
-```
-
 ## Pull Requests
 
 - keep changes focused