feat: add scoped Kubernetes manifest linting

[zeitlinger]

Summary

• add report-only kube-linter support for explicitly selected Kubernetes manifests
• default to conventional Kubernetes directories while excluding unrelated YAML and Compose files
• add configuration support, generated documentation, tool pins, and focused tests

Split from #430 so the kube-linter integration can be reviewed independently.

Validation

• mise run generate
• mise run lint:fix
• mise exec -- cargo test

[zeitlinger]

Pre-release consumer validation is running in grafana/docker-otel-lgtm#1635. Flint discovers the real k8s/lgtm.yaml manifest, and the repository now documents intentional exclusions for five production-oriented checks that do not fit its development/demo deployment. Focused kube-linter, full Flint lint, and all 38 unit tests pass locally.

[Copilot]

Pull request overview

Adds first-class, scoped kube-linter integration to Flint, aimed at linting Kubernetes manifests without accidentally sweeping in unrelated YAML (e.g., Docker Compose).

Changes:

• Add a new native kube-linter check type with conventional directory defaults plus explicit path/config support.
• Wire kube-linter into the registry, generated docs/README tables, and tool pinning + Renovate tracking.
• Add focused end-to-end fixture cases covering selection behavior.

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/cases/kube-linter/selection/test.toml	E2E case asserting kube-linter receives only selected manifest paths
tests/cases/kube-linter/selection/files/mise.toml	Fixture pins kube-linter for the selection case
tests/cases/kube-linter/selection/files/k8s/deployment.yaml	Sample Kubernetes manifest used for selection
tests/cases/kube-linter/selection/files/compose.yaml	Non-Kubernetes YAML fixture to ensure it’s excluded
tests/cases/kube-linter/clean/test.toml	E2E “clean” baseline for kube-linter
tests/cases/kube-linter/clean/files/mise.toml	Fixture pins kube-linter for the clean case
tests/cases/kube-linter/clean/files/k8s/configmap.yaml	Sample Kubernetes manifest for the clean case
src/registry/checks.rs	Registers the new kube-linter check, patterns, and generated docs metadata
src/main.rs	Updates the linters table fixture to include kube-linter
src/linters/mod.rs	Exposes the new kube-linter linter module
src/linters/kube_linter.rs	Implements manifest selection + kube-linter invocation (new native check)
src/config.rs	Adds [checks.kube-linter] configuration schema
README.md	Adds kube-linter to the Tooling/CI overview table
mise.toml	Pins kube-linter version for the repo toolchain
docs/linters.md	Adds generated kube-linter documentation section
default.json	Tracks kube-linter in the default tool set
.github/renovate.json5	Adds kube-linter to Renovate-managed dependency list
.github/renovate-tracked-deps.json	Adds kube-linter datasource/package mapping for Renovate

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