Fix docs and review-prompt wording defects (issue #1872)

> [!CAUTION]
> Protected files were modified in this change.
> This pull request is in `request_review` mode and requires explicit human scrutiny before merge.
>
> Protected files: `README.md`, `.github/workflows/gh-aw-estc-docs-pr-review.lock.yml`, `.github/workflows/gh-aw-fragments/safe-output-submit-review.md`, `.github/workflows/gh-aw-mention-in-pr-no-sandbox.lock.yml`, `.github/workflows/gh-aw-mention-in-pr.lock.yml`, `.github/workflows/gh-aw-pr-review.lock.yml`, `.github/workflows/gh-aw-pr-review.md`

## Summary
- fix the broken quick-setup sentence in `gh-agent-workflows/README.md`
- clarify that `CLAUDE_CODE_OAUTH_TOKEN` is no longer required and remove incorrect `either` phrasing in `docs/migration-guide.md`
- replace `approve/request-changes decision` with `approval/request-changes decision` in PR review source prompt files
- update Go prerequisite wording in `docs/developing.md` to match current setup guidance
- regenerate affected compiled workflow lock files via `make compile`

## Validation
- `make compile`
- `make lint`

Closes \#1872.

> [!WARNING]
>
> Firewall blocked 1 domain
>
> The following domain was blocked by the firewall during workflow execution:
>
> - `models.dev`
>> To allow these domains, add them to the `network.allowed` list in your workflow frontmatter:
>
> ```yaml
> network:
> allowed:
> - defaults
> - "models.dev"
> ```
>
> See [Network Configuration](https://github.github.com/gh-aw/reference/network/) for more information.
>
>

---
[What is this?](https://ela.st/github-ai-tools) | [From workflow: Trigger Text Auditor](https://github.com/elastic/ai-github-actions/actions/runs/32373687396)

Give us feedback! React with 🚀 if perfect, 👍 if helpful, 👎 if not.

---

> [!NOTE]
> This was originally intended as a pull request, but the git push operation failed.
>
> **Original error:** pushSignedCommits: refusing unsigned push for branch 'fix-issue-1872-text-defects-a1200b058152adab': Signed-commit payload violates file-protection policy (request_review): gh-agent-workflows/README.md, .github/workflows/gh-aw-estc-docs-pr-review.lock.yml, .github/workflows/gh-aw-fragments/safe-output-submit-review.md, .github/workflows/gh-aw-mention-in-pr-no-sandbox.lock.yml, .github/workflows/gh-aw-mention-in-pr.lock.yml, .github/workflows/gh-aw-pr-review.lock.yml, .github/workflows/gh-aw-pr-review.md
>
> **Workflow Run:** [View run details and download bundle artifact](https://github.com/elastic/ai-github-actions/actions/runs/32373687396)
>
> The bundle file is available in the `agent` artifact in the workflow run linked above.

To create a pull request with the changes:

```sh
# Download the artifact from the workflow run
gh run download 32373687396 -n agent -D /tmp/agent-32373687396

# Fetch the bundle into a temporary ref, then update the local branch
git fetch /tmp/agent-32373687396/aw-fix-issue-1872-text-defects.bundle refs/heads/fix-issue-1872-text-defects:refs/bundles/create-pr-fix-issue-1872-text-defects-a1200b058152adab-a2e84913
git update-ref refs/heads/fix-issue-1872-text-defects-a1200b058152adab refs/bundles/create-pr-fix-issue-1872-text-defects-a1200b058152adab-a2e84913
git checkout fix-issue-1872-text-defects-a1200b058152adab
# Ensure the working tree matches the updated branch
git reset --hard
# Remove the temporary bundle ref
git update-ref -d refs/bundles/create-pr-fix-issue-1872-text-defects-a1200b058152adab-a2e84913

# Push the branch to origin
git push origin fix-issue-1872-text-defects-a1200b058152adab

# Create the pull request
gh pr create --title 'Fix docs and review-prompt wording defects (issue #1872)' --base main --head fix-issue-1872-text-defects-a1200b058152adab --repo elastic/ai-github-actions
```

Start with the files named in the summary: gh-agent-workflows/README.md, docs/migration-guide.md, docs/developing.md, and the PR review prompt and lock files. Review the existing wording, then run make compile and make lint; done means the documented text and prompt wording are corrected and the affected compiled lock files are regenerated.

Written by the indexing model from the issue text.