chore: remove CODEOWNERS chassis and the code-owner review gate

The repo is a 2-person team where both maintainers own every path, so the
CODEOWNERS machinery (generated CODEOWNERS, roles yml, render script, the two
drift/hand-edit CI jobs) gated nothing real while adding friction: every PR
showed "Review required" and own-PRs merged only via admin/bypass override.

Remove the whole chassis and drop the review gate:
- delete .github/CODEOWNERS, codeowners-roles.yml, render-codeowners.py,
  the CODEOWNERS workflow, and docs/dev/codeowners.md
- branch-protection.json: drop the two CODEOWNERS required status checks,
  set require_code_owner_reviews=false and required_approving_review_count=0
  (CI checks are the gate; maintainers merge their own PRs once green)
- scrub CODEOWNERS references from AGENTS.md, docs indexes, branch-protection
  and ci docs, GOVERNANCE.md, and CONTRIBUTING.md

The policy change is inert until an admin runs scripts/apply-branch-protection.sh.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/dev/ci.md

@@ -3,7 +3,7 @@
 `.github/workflows/`:
 
 - **ci.yml**: text-only changes skip; otherwise `cargo test --workspace --locked` on ubuntu-latest with protobuf compiler. OpenAPI-drift check that auto-commits the regenerated `openapi.json` for same-repository PRs. Also runs the AGENTS.md cross-link integrity check (`scripts/check-agents-md.sh`).
-  - **`Test Workspace` does not run on pull requests.** The job is gated `if: github.event_name != 'pull_request'`, so the full workspace + failpoints suite runs only on push to `main` (post-merge), on `v*` tags, and on manual `workflow_dispatch`. This was a deliberate PR-latency trade-off — it was the slowest gate (~15min warm, up to the 75min cold ceiling). `RustFS S3 Integration` `needs: test`, so it is push-/dispatch-only for the same reason. The fast PR gates remain: `Classify Changes`, `Check AGENTS.md Links`, `Test omnigraph-server --features aws`, and the two CODEOWNERS checks. `Test Workspace` is correspondingly **not** in the required-check list (`.github/branch-protection.json`); see [branch-protection.md](branch-protection.md).
+  - **`Test Workspace` does not run on pull requests.** The job is gated `if: github.event_name != 'pull_request'`, so the full workspace + failpoints suite runs only on push to `main` (post-merge), on `v*` tags, and on manual `workflow_dispatch`. This was a deliberate PR-latency trade-off — it was the slowest gate (~15min warm, up to the 75min cold ceiling). `RustFS S3 Integration` `needs: test`, so it is push-/dispatch-only for the same reason. The fast PR gates remain: `Classify Changes`, `Check AGENTS.md Links`, and `Test omnigraph-server --features aws`. `Test Workspace` is correspondingly **not** in the required-check list (`.github/branch-protection.json`); see [branch-protection.md](branch-protection.md).
   - **Consequences to internalize:** (1) a regression that the suite would catch now lands on `main` and turns the post-merge run red, rather than being blocked pre-merge — `main` can briefly break, so run `cargo test --workspace --locked` locally before merging anything non-trivial, or trigger this workflow on your branch via the Actions "Run workflow" button. (2) `openapi.json` is no longer auto-regenerated on PRs (that step is inside the `test` job); for server/API changes, regenerate it locally with `OMNIGRAPH_UPDATE_OPENAPI=1 cargo test -p omnigraph-server --test openapi` and commit it, or the strict drift check fails the post-merge `main` run.
   - **Applying this policy:** removing `Test Workspace` from the JSON is inert until an admin runs `./scripts/apply-branch-protection.sh`. **Run it immediately after this change merges** — until then GitHub still requires a `Test Workspace` context that no longer reports on PRs, which leaves every open PR permanently pending (the job-never-reports trap).
 - **AWS feature build job**: `cargo build/test -p omnigraph-server --features aws` on ubuntu-latest.