harden helm pending checks and CRD coverage

[atkrad]

Summary

• Reject stuck pending Helm releases with a typed Status.IsPending check before chart prep, instead of fragile string matching in wrapHelmError.
• Add CRD lifecycle e2e coverage, chart-cache key invariant tests, and install-after-CRD-step unit coverage; consolidate Session client cloning.
• Document CRD non-atomic failure modes and tighten the comparison note about where the Helm abstraction thins.

Test plan

• Unit tests added/updated (internal/helm, internal/cmd/deploy, internal/session)
• Scenario under scenarios/ (if behavior changes)
• golangci-lint / pre-commit clean on commit
• Manual smoke (command + expected result), if user-facing
• E2E Kind suite (go test -tags=e2e ./internal/e2e/) for TestCRDLifecycle

Labels

• One of: kind/feature, kind/bug, kind/docs, kind/chore → kind/bug
• Add breaking-change if this breaks existing CLI or config behavior
• Add skip-changelog for internal-only PRs that should not appear in notes

Checklist

• Title is short and imperative (matches commit style)
• Docs updated (docs/comparison.md, docs/custom-manifests-and-crds.md)
• No secrets or local-only paths in the diff

[codecov]

Codecov Report

❌ Patch coverage is 80.64516% with 6 lines in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
internal/helm/helm.go	77.77%	6 Missing ⚠️

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