feat: integrate embedded-cluster CLI lint into release lint pipeline

[emosbaugh]

Summary

• Adds EC lint as an opt-in linter (disabled by default) that runs the embedded-cluster CLI against manifest files alongside existing Helm, Preflight, and Support Bundle linters
• Automatically discovers the EC version from the embeddedcluster.replicated.com/v1beta1 Config manifest (spec.version) — no separate config needed; supports multi-document YAML files
• Downloads the EC binary from S3 (https://tf-embedded-cluster-binaries.s3.us-east-1.amazonaws.com/releases/{version}-{os}-{arch}.tgz) and caches it alongside other tools; version resolution via replicated.app/ping is not supported for EC so the fallback path is skipped
• Supports binary-path config field and REPLICATED_EMBEDDED_CLUSTER_BINARY_PATH env var to bypass the resolver — version discovery is skipped when a binary path is provided
• Configurable disable-checks list with defaults (helmchart-archive, ecconfig-helmchart-archive)
• Linter config unified: all linters use LinterConfig (or ECLinterConfig which embeds it); ApplyDefaults is the single source of truth for which linters are on/off by default — nil is a transient parse state, never reaches IsEnabled() at runtime
• In auto-discovery mode, the "no lintable resources" early return is skipped when EC linting is enabled, since EC lints a distinct set of files not found by traditional discovery

Example config

repl-lint:
  linters:
    embedded-cluster:
      disabled: false
      # optional overrides:
      # binary-path: /path/to/cli
      # disable-checks:
      #   - preflight-v1beta2

Test plan

• Run replicated release lint without EC config — EC section shows as disabled
• Enable EC linting in .replicated, point at a manifests dir with an EmbeddedCluster/Config manifest — version is auto-discovered, binary is downloaded and linting runs
• Set REPLICATED_EMBEDDED_CLUSTER_BINARY_PATH to a local binary — resolver is bypassed, version discovery is skipped
• JSON output includes embedded_cluster_results field
• EC lint errors cause overall linting failed exit code
• Auto-discovery mode with only EC manifests (no charts/preflights) — EC linting still runs

🤖 Generated with Claude Code

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 788fa97. Configure here.}