ai: add Gemini Code Assist configuration for code reviews

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Miguel Duarte Barroso <mdbarroso@redhat.com>

Author: maiqueb

.gemini/config.yaml

@@ -0,0 +1,14 @@
+code_review:
+  comment_severity_threshold: MEDIUM
+  pull_request_guidelines:
+    - file: .gemini/styleguide.md
+
+  ignore_patterns:
+    - "vendor/**"
+    - "dist/**"
+    - "bin/**"
+    - "config/**"
+    - ".output/**"
+    - "**/*.pb.go"
+    - "**/*_generated.go"
+    - "**/*zz_generated*.go"

.gemini/styleguide.md

@@ -0,0 +1,84 @@
+# Code Review Style Guide
+
+This is a Kubebuilder-based Kubernetes controller and mutating webhook that manages
+persistent IPAM claims for KubeVirt virtual machines. It implements the multi-network
+de-facto standard v1.3 for IPAM extensions, working with OVN-Kubernetes CNI.
+
+## Architecture
+
+- VirtualMachineReconciler (`pkg/vmnetworkscontroller/`) — watches KubeVirt VM objects,
+  creates/manages IPAMClaim lifecycle, handles VM deletion with finalizers.
+- VirtualMachineInstanceReconciler (`pkg/vminetworkscontroller/`) — watches VMI objects,
+  manages IPAM claims for running instances.
+- Pod Mutation Webhook (`pkg/ipamclaimswebhook/`) — mutates virt-launcher pods to request
+  persistent IPs by reading IPAM claims and annotating pods.
+
+## Code Readability: Line of Sight
+
+Prefer code that reads vertically with minimal nesting:
+
+- Keep the happy path left-aligned with minimal indentation.
+- Use early returns to exit as soon as conditions are met.
+- Avoid else-returns: invert conditions and return early instead.
+- Break large functions into smaller, single-purpose functions.
+
+Prefer:
+
+```go
+func Process(data string) error {
+    if data == "" {
+        return errors.New("empty data")
+    }
+    if !isValid(data) {
+        return errors.New("invalid data")
+    }
+    return doWork(data)
+}
+```
+
+Over deeply nested if-else blocks.
+
+## Line Length
+
+Lines should not exceed 120 characters. Flag lines that are significantly longer.
+
+## Package Organization
+
+- Package names must be descriptive and single-word — avoid `util`, `common`, `lib`, `misc`, `helpers`.
+- Primary file should be named after the package (e.g., `network.go` in package `network`).
+- In all files: exported/main functions first, internal helpers at the bottom.
+- This applies to test files too: test functions first, helper functions at the bottom.
+
+## Error Handling
+
+- Use `errors.Is` and `errors.As` for error type checking — never compare error strings.
+- Wrap errors with `fmt.Errorf` and `%w` to preserve the error chain.
+- Each layer should add context about what operation failed.
+
+## Dependency Management
+
+- Environment variables must only be read in `main()` and passed explicitly via parameters
+  or config structs. Flag any package that reads `os.Getenv` or `os.LookupEnv` directly.
+- Use pointer arguments only when the function needs to modify the argument.
+- Use value arguments for read-only parameters.
+
+## Security
+
+- Apply the principle of least privilege for RBAC markers and service account permissions.
+- Validate all input at system boundaries (user input, external API responses).
+
+## Testing
+
+- Unit tests use Ginkgo v2 + Gomega with envtest. New logic should have test coverage.
+- Flag test files that place helper functions before the test functions (wrong order).
+
+## Code Generation
+
+- If kubebuilder markers (`+kubebuilder:rbac`, `+kubebuilder:webhook`, etc.) are modified,
+  remind the author to run `make manifests generate`.
+- If `dist/install.yaml` may be affected, remind the author to run `make build-installer`.
+
+## Vendor
+
+- If `go.mod` or `go.sum` are changed, the vendor directory must also be updated
+  (`make vendor`). CI validates this with `make check-vendoring`.