docs: add Units module migration investigation and plan

[JeffySam]

Description

This pull request adds documentation describing the current state and planned approach for migrating the Units module from AngularJS (CoffeeScript) to Angular (TypeScript).

The documentation focuses on the migration of the Units state hierarchy, including the legacy state aggregator (units/states/states.coffee) and its Angular replacement. It captures the current migration status, identifies remaining AngularJS states, and outlines a parent-first migration strategy to safely unblock downstream work.

Two documents are included:

• Units Module Migration Investigation — documents the existing implementation, identifies incomplete or blocking states, and records findings from the investigation phase.
• Units Module Migration Plan — defines the recommended migration sequence, validation steps, risks, and success criteria for completing the Units module migration.

This PR is documentation-only and does not modify application code.

Fixes: N/A

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Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (update or new)

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How Has This Been Tested?

• Verified that both documents render correctly in the documentation site
• Confirmed file placement follows the existing documentation structure
• Reviewed headings, lists, and code references for clarity and accuracy
• Cross-checked content against the current codebase and migration state

No runtime or build testing was required, as this PR contains documentation only.

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Testing Checklist

• Have run npm run format (not applicable — no code changes)
• Have run npm run build (not applicable — no code changes)
• Have run npm run dev and/or npm run preview, using:
• Chrome
• Safari
• Firefox

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Checklist

• My changes follow the style guidelines of this project
• I have performed a self-review of my own changes
• I have ensured documentation is clear, accurate, and complete
• I have made corresponding documentation updates where required
• My changes generate no new warnings
• I have requested a review on this Pull Request

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[SteveDala]

LGTM. The plan to migrate the units module seems cogent and well thought through. Although I'm sure more challenges will arise as a result of the attempt to migrate this module, this represents a good starting point to do so.

[SteveDala]

Hi @JeffySam, in your development environment, please execute npm run format.

Checking formatting...
[warn] src/content/docs/Products/OnTrack/Documentation/Front End Migration/Migration/UNITS_MODULE_MIGRATION_INVESTIGATION.md
[warn] src/content/docs/Products/OnTrack/Documentation/Front End Migration/Migration/UNITS_MODULE_MIGRATION_PLAN.md
[warn] Code style issues found in 2 files. Run Prettier with --write to fix.
Error: Process completed with exit code 1.

[JeffySam]

hi @SteveDala i did execute npm run format like u said

[SteveDala]

@JeffySam please make sure your changes are based on the latest upstream changes to main.