feat: Use relative paths to reference sub-actions in composite actions

[smockle]

Fixes https://github.com/github/continuous-ai-for-accessibility/issues/87 (Hubber access only)
Fixes https://github.com/github/continuous-ai-for-accessibility/issues/81 (Hubber access only)

Problem

uses: github/accessibility-scanner@main currently fails with the following error—

Error: Can't find 'action.yml', 'action.yaml' or 'Dockerfile' under '/home/runner/work/accessibility-sandbox/accessibility-sandbox/.github/actions/gh-cache/cache'. Did you forget to run actions/checkout before running your local action?

—this PR makes it work.

Solution

This PR basically moves the preparatory cp workflow step we used to require into the composite action(s) itself.

This PR is a superior alternative to c262469:

1. It restores our ability to merge main directly into v2, which simplifies backports (e.g. dependency updates that Dependabot opens for main).
2. It means referencing a point release (e.g. uses: github/[email protected]) only runs code from that release (rather than a mix of v2.4.0 and (newer) v2 code).

Testing

• I tested using uses: github/accessibility-scanner@smockle/restore-relative-paths, and it worked: https://github.com/github/accessibility-sandbox/actions/runs/18943849865 (Hubber access only)
• I tested using a sub-action directly (e.g. uses: github/accessibility-scanner/.github/actions/gh-cache/cache@smockle/restore-relative-paths), and it worked: https://github.com/github/accessibility-sandbox/actions/runs/18945624950 (Hubber access only)
• The “Test” CI check passed: https://github.com/github/accessibility-scanner/actions/runs/18944419202/job/54092648187?pr=59

[Copilot]

Pull Request Overview

This PR refactors the action reference mechanism to enable nested composite actions to reference sub-actions. Instead of using relative paths like ./.github/actions/..., the actions are now copied to a centralized location (/home/runner/work/_actions/current/.github/actions/) and referenced via ./../../_actions/current/.github/actions/....

• Added setup steps to copy sub-actions to a centralized location using rsync
• Updated all action references from relative ./.github/actions/ paths to ./../../_actions/current/.github/actions/
• Changed quote style for consistency in one default value

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
action.yml	Added sub-action setup step and updated all 6 action references to use the centralized path
.github/actions/gh-cache/cache/action.yml	Added sub-action setup step and updated 2 action references, plus a quote style consistency fix

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[Copilot]

The hardcoded absolute path /home/runner/work/_actions/current/ assumes a specific runner directory structure that may not be portable across different environments or runner types (e.g., self-hosted runners). Consider using a relative path or environment variable like $RUNNER_TEMP to make this more portable.

Suggested change

	mkdir -p /home/runner/work/_actions/current/.github/actions
	rsync -a .github/actions/ /home/runner/work/_actions/current/.github/actions/
	ls -ltra /home/runner/work/_actions/current/.github/actions
	mkdir -p "${{ github.action_path }}/.github/actions"
	rsync -a .github/actions/ "${{ github.action_path }}/.github/actions/"
	ls -ltra "${{ github.action_path }}/.github/actions"

[Copilot]

The hardcoded absolute path /home/runner/work/_actions/current/ assumes a specific runner directory structure that may not be portable across different environments or runner types (e.g., self-hosted runners). Consider using a relative path or environment variable like $RUNNER_TEMP to make this more portable.