chore: remove Bazel build support

.gitignore

@@ -236,6 +236,3 @@ scripts/lint-mermaid/node_modules/
 # Nix
 /result
 /result-*
-
-# Bazel
-bazel-*

CONTRIBUTING.md

@@ -296,24 +296,6 @@ Project requirements:
 - Python 3.11+
 - Docker (running)
 
-### Optional: Bazel (experimental)
-
-Install [Bazelisk](https://github.com/bazelbuild/bazelisk), which auto-downloads the Bazel version pinned in `.bazelversion`:
-
-```bash
-# macOS
-brew install bazelisk
-
-# npm (any platform)
-npm install -g @bazel/bazelisk
-```
-
-Bazel builds Z3 from source, so no system Z3 installation is needed when using Bazel. If you have previously built with Cargo, add Cargo's output directory to `.bazelignore` to prevent conflicts:
-
-```bash
-echo "target" >> .bazelignore
-```
-
 ### Z3 installation
 
 The `openshell-prover` crate links against Z3. On macOS and Linux, install the
@@ -431,26 +413,6 @@ These are the primary `mise` tasks for day-to-day development:
 | `mise run helm:docs` | Regenerate the Helm chart README |
 | `mise run clean` | Clean build artifacts |
 
-### Bazel targets (experimental)
-
-> [!IMPORTANT]
-> Bazel support is experimental and under evaluation via [RFC 0012](https://github.com/NVIDIA/OpenShell/pull/2543).
-> It may be removed at any time depending on the RFC outcome.
-> Feedback is welcome: [open an issue](https://github.com/NVIDIA/OpenShell/issues/new) or find us on CNCF Slack in [#openshell-dev](https://cloud-native.slack.com/archives/openshell-dev).
-
-The following Bazel commands are available alongside the mise tasks above. Cargo and mise remain the primary build system.
-
-| Task | Bazel command | Notes |
-| ---- | ------------- | ----- |
-| Build everything | `bazel build //...` | All crates and protos |
-| Run all tests | `bazel test //...` | Unit tests only, no E2E |
-| Build the CLI | `bazel build //crates/openshell-cli:openshell` | |
-| Build the gateway | `bazel build //crates/openshell-server:openshell-gateway` | |
-| Build the supervisor | `bazel build //crates/openshell-sandbox:openshell-sandbox-bin` | |
-| Clean | `bazel clean` | |
-
-Bazel does not yet cover `mise run gateway`, `mise run sandbox`, `mise run e2e`, `mise run docs`, or `mise run helm:docs`. Those are runtime and infrastructure tasks that remain with mise. Additional Bazel targets will be added over time as the experiment progresses.
-
 ## Project Structure
 
 | Path | Purpose |