feat(terraform_plan): clearer reason messages — resource, action and attribute in every result

[refeed]

In flight as #287 — land it. NotEquals printed `"public-read"` is not equal to `"private"`
and nothing else; with 30 buckets that is 30 identical lines. After the change every terraform_plan
message names the resource address, its planned action and the attribute —
[aws_s3_bucket.example (create)] acl: … — via an optional provider context key rendered by
format_context_prefix() and kept as structured fields on the result.

Acceptance. #287 merged on main; CHANGELOG entry; tests/example-output.jsonc reflects the
new shape.