Enhance alignment visualization and comparison features

[BeckettFrey]

This pull request introduces two new pipeline steps—Alignment Viewer and Alignment Comparison—across all pipeline configuration profiles, updates the workflow documentation and UI to reflect these new steps, and adds the required dependency for alignment comparison plots. It also updates the GUI to register and handle these new stackers, and makes minor improvements to test reliability and UI labels.

Pipeline step additions and configuration:

• Added ViewerStacker ("View Alignments") and ComparisonStacker ("Compare Alignments") as new steps in the pipeline definitions for all profiles, allowing users to inspect and compare forced alignments with detailed documentation and workflow updates. [1] [2] [3] [4] [5]
• Updated step lettering throughout documentation and UI from Ⓓ (PLLR Extraction) to Ⓕ, reflecting the insertion of the new steps. [1] [2] [3] [4]

Dependency management:

• Added alignment-comparison-plots as a new dependency and specified its GitHub source for installation. [1] [2]

GUI enhancements:

• Registered ViewerStacker and ComparisonStacker in the GUI stacker registry, and ensured their dataset reload methods are called when appropriate. [1] [2] [3] [4]
• Updated page titles for stackers to remove step letters for consistency and clarity. [1] [2] [3]

Testing improvements:

• Improved reliability of worker thread tests by explicitly waiting for worker completion after signal emission. [1] [2] [3] [4]