chore: pin stale branch action to release tag and add dry-run to release pipeline

[GoogilyBoogily]

Summary

Two unrelated housekeeping changes.

stale-cleanup.yml

• fpicalausa/remove-stale-branches was pinned to a raw commit SHA (7c4f2afe...). Updated to the latest release tag v2.6.1 for auditability and easier dependency tracking. (actions/stale@v10 is already on the latest major version — no change needed.)

release-pipeline.yml

• Adds a dry-run boolean input (default false) to the reusable workflow.
• Threads it through to all three publish steps: version-bump, npm-publish, and release-notes.
• Enables safe end-to-end testing of the full pipeline without publishing to npm or creating a GitHub release.

Test plan

• Trigger release-pipeline with dry-run: true — pipeline runs fully, no npm publish, no GitHub release created
• Stale cleanup runs without errors on next scheduled run

[Copilot]

Pull request overview

Two unrelated housekeeping changes: pin the remove-stale-branches action to a release tag for auditability, and add a dry-run boolean input to the reusable release-pipeline.yml plumbed through to the three publish steps.

Changes:

• Pin fpicalausa/remove-stale-branches from a raw SHA to v2.6.1.
• Add dry-run input (default false) on release-pipeline.yml and forward it to version-bump, npm-publish, and release-notes.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
.github/workflows/stale-cleanup.yml	Updates third-party action pin from commit SHA to release tag v2.6.1.
.github/workflows/release-pipeline.yml	Adds dry-run workflow_call input and threads it through to the three downstream composite actions.

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