fix(action): improve ensure-json-report error messages

[skoshx]

Problem

When the GitHub Action receives a missing, malformed, or incompatible CLI report, ensure-json-report.mjs replaces it with a generic fallback. The fallback hides whether the CLI produced no file, empty output, invalid JSON, an unsupported schema, or an incomplete report.

Solution

• Emit a specific, actionable fallback for each failure class.
• Keep parser details and filesystem paths out of PR-facing error text.
• Continue accepting report schema versions 1, 2, and 3.
• Always write the existing schema-v3 fallback shape on failure.
• Remove the npm-package Changeset: this changes only the independently versioned GitHub Action.

Validation

• Added 10 focused tests covering every supported schema plus missing, empty, non-JSON, non-object, unsupported-schema, and missing-ok reports.
• Full repository tests, lint, typecheck, formatting, and JSON-report smoke test pass locally.
• React Doctor reports 100/100 on the changed scope.

Release note

This touches scripts/ensure-json-report.mjs, so it needs a patch GitHub Action release after merge. It does not require an npm package release.

Closes #1331

[github-actions]

📦 GitHub Action release recommended

This PR changes the React Doctor GitHub Action's release surface:

• scripts/ensure-json-report.mjs

The composite action is versioned independently from the npm packages, so it
needs its own git tag once this merges. Based on the PR title, this looks like
a patch bump (fix / refactor / chore / docs): v2.2.8 → v2.2.9.

After merging, cut the tag from the merge commit on main (tags are GPG-signed
annotated tags, so run this locally where your signing key is configured):

git checkout main && git pull --ff-only
merge_commit=$(git rev-parse HEAD)
git tag -a v2.2.9 "$merge_commit" -m "react-doctor action v2.2.9"
git tag -fa v2 "$merge_commit" -m "react-doctor action v2 (floating major -> v2.2.9)"
git push origin v2.2.9
git push --force origin v2   # moves only the floating major pointer

_{This bump can also be performed automatically on merge — set the repo
variable AUTO_BUMP_ACTION_TAG=true. Recommendation by the Action Version Bump workflow.}

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/eslint-plugin-react-doctor@1332

npm i https://pkg.pr.new/oxlint-plugin-react-doctor@1332

npm i https://pkg.pr.new/react-doctor@1332

commit: 0d59eb9

[github-actions]

React Doctor found no new issues. 🎉

_{Reviewed by React Doctor for commit 0d59eb9.}