add drift from previous to live

[atkrad]

Summary

• An existing release now reports drift from the stored manifest to live objects.
• Drift only gets and lists. It does not change the Helm action, resource changes, tasks, or summary.
• A fresh install does not read the cluster. deployah plan still uses the older plan.

Test plan

• Unit tests added/updated
• Scenario under scenarios/ (if behavior changes)
• nix run .#lint / pre-commit clean
• Manual smoke (command + expected result), if user-facing

Pre-commit ran gofmt, golangci-lint, and the other hooks. go test ./internal/plan/... passed, including -race. The e2e test compiles. It was not run, because the current kubectl context is a production cluster.

Labels

• One of: kind/feature, kind/bug, kind/docs, kind/chore
• 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 / CLI help updated when user-facing (README.md, docs/cli/)
• No secrets or local-only paths in the diff

[codecov]

Codecov Report

❌ Patch coverage is 88.48168% with 66 lines in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
internal/plan/semantic_drift.go	90.45%	27 Missing ⚠️
internal/plan/view/human.go	79.10%	14 Missing ⚠️
internal/plan/view/project.go	79.59%	10 Missing ⚠️
internal/plan/semantic_build.go	68.42%	6 Missing ⚠️
internal/plan/live_reader.go	89.28%	3 Missing ⚠️
internal/plan/semantic/drift.go	97.59%	2 Missing ⚠️
internal/plan/view/prepare.go	75.00%	2 Missing ⚠️
internal/plan/view/redact.go	90.47%	2 Missing ⚠️

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