feat(copyright): preserve less-normalized output by default

[mstykow]

Summary

• keep a less-normalized file-level copyright string in files[].copyrights[].copyright by default while still carrying normalized shadow values internally for tallies, shaping, summary fallback, and package metadata promotion
• add a generic --compat-mode scancode projection so parity-sensitive workflows can still emit ScanCode-style rendered copyright strings without changing the public field shape
• teach compare workflows to ignore the intentional All rights reserved / trailing-punctuation rendering delta while still surfacing real copyright-count and value differences

Scope and exclusions

• Included: copyright model/projection changes, compare normalization, replay/cache handling, targeted tests, and scoped documentation updates
• Explicit exclusions: no new output field was added, no separate sidecar artifact was introduced, and no broad fixture regeneration was done

Intentional differences from Python

• native Provenant output now keeps a less-normalized file-level copyright string in files[].copyrights[].copyright; users can opt back into ScanCode-style rendering with --compat-mode scancode
• the output shape stays the same; this is a rendering-policy difference, not a schema fork

Concrete examples

From a real Kubernetes file:
vendor/k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json/errors.go

Source header:
// Copyright 2020 The Go Authors. All rights reserved.

• native/default Provenant output:
  Copyright 2020 The Go Authors. All rights reserved.
• --compat-mode scancode output:
  Copyright 2020 The Go Authors

From another real Kubernetes file:
vendor/k8s.io/kube-openapi/pkg/aggregator/aggregator.go

Source header:
Copyright 2017 The Kubernetes Authors.

• native/default Provenant output:
  Copyright 2017 The Kubernetes Authors.
• --compat-mode scancode output:
  Copyright 2017 The Kubernetes Authors

Follow-up work

• Created or intentionally deferred: if future compatibility bundles grow beyond copyright rendering, reevaluate whether --from-json should preserve more compatibility metadata than the current output shape carries