Support workflow consumers without a local DevTools dependency

[coisa]

Related Issue

Closes #303

Motivation / Context

• reusable workflows currently assume composer dev-tools exists in the consumer repository;
• workflow-only consumers need a deterministic fallback tied to the checked-out DevTools workflow source instead of an unrelated implicit global version.

Changes

• reworked .github/actions/php/setup-composer to use ramsey/composer-install for generic Composer installs, skip the consumer install when no composer.json is present, and expose a shared dev-tools runtime plus autoload environment variables;
• updated reusable workflows and packaged changelog helpers to call dev-tools from the shared runtime instead of shelling into composer dev-tools;
• documented the local-vs-workflow runtime behavior and added regression coverage for local and fallback runtime resolution.

Verification

• composer dev-tools
• Focused command(s):
  • composer dev-tools tests -- --filter='SetupComposerActionTest'
  • composer dev-tools code-style
  • composer dev-tools phpdoc
• Manual verification:
  • not run against a live GitHub Actions workflow from this local checkout

Documentation / Generated Output

• README updated
• docs/ updated
• Generated or synchronized output reviewed

Changelog

• Added a notable CHANGELOG.md entry

Reviewer Notes

• .github/wiki was already dirty in the local checkout and was intentionally kept out of this branch and commit.
• The fallback runtime is resolved from the checked-out .dev-tools-actions source checkout, keeping workflow behavior aligned with the workflow ref used by the reusable workflow.

[chatgpt-codex-connector]

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[github-actions]

🚀 Preview is available for this pull request.

• Docs: https://php-fast-forward.github.io/dev-tools/previews/pr-307/
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• Metrics: https://php-fast-forward.github.io/dev-tools/previews/pr-307/metrics/

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 0dc32afaca

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[coisa]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Hooray!

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

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• Mark a draft as ready
• Comment "@codex review".

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