[Bug]: Include root internal packages in release changed-file ownership #262

Problem

Release preparation assigns top-level internal/ source files to repository instead of the root Go module. affected_modules recognizes commons/, root-level Go files and go.mod/go.sum, but misses the root module's private packages. module_changes consequently omits those source files from the root changed-file disclosure.

Reproduction

For the v1.3.0 preparation source 5667eb3b249c4761a13a5cb10f2a9d59988edd4a, comparing v1.2.0 also changes:

• internal/jsonvalue/snapshot.go
• internal/jsonvalue/snapshot_benchmark_test.go
• internal/jsonvalue/snapshot_test.go

The root module's frozen changed_files list contains only go.mod. The root performance summary from #253 is present, and the release still packages the new code. All maintained modules already classify as Updated because of the Go directive update. This is a disclosure/ownership defect, not a missing runtime fix or a security-release blocker. Refs #255 and #261.

Expected behavior

• Root private Go package changes belong to the root module, while website/docs/tooling stay repository-only.
• Deepest registered module ownership remains intact, including future nested internal modules.
• Cover edits, additions, deletions and renamed root internal files with real Git history tests.
• Preserve validation/rendering of existing frozen plans. Introduce explicit ownership-version metadata if required; never rewrite published tags or old notes silently.

Validation

Run the existing release automation/notes tests with CGO_ENABLED=0 for all Go subprocesses. Add a regression for root-only internal changes and verify both their changed-file list and release-note classification.