fix: Fix stale watched action data overwriting proposal actions after remove/add

[milosh86]

Description

useFieldArray's fields update synchronously inside remove()/append(), but useWatch only catches up a render later. Comparing array length alone isn't enough to detect that lag: deleting one action and adding a different one leaves the array length unchanged, so a stale watchedAction describing the just-deleted action can slip through — overwriting the new action's type and silently mounting the wrong view populated with the previous action's data.

This replaces the length-based staleness check with a fieldId comparison (unique per action instance), which catches the lag even when the length coincidentally matches again.

Type of Change

• Major: Breaking change (change that would cause existing functionality to not work as expected)
• Minor: Feature (non-breaking change which adds new functionality)
• Patch: Enhancement (non-breaking change to an existing feature)
• Patch: Bug fix (non-breaking change which fixes an issue)

Developer Checklist:

• Manually smoke tested the functionality in a preview or locally
• Confirmed there are no new warnings or errors in the browser console
• (For User Stories only) Double-checked that all Acceptance Criteria are satisfied
• Confirmed there are no new warnings on automated tests
• Merged and published any dependent changes in downstream modules
• Selected the correct base branch
• Commented the code in hard-to-understand areas
• Followed the code style guidelines of this project
• Reviewed that the Files Changed in Github's UI reflect my intended changes
• Confirmed the pipeline checks are not failing

Review Checklist:

• (For User Stories only) Tested in a preview or locally that all Acceptance Criteria are satisfied
• Confirmed that changes follow the code style guidelines of this project

[github-actions]

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E2E results (preview)

Smoke

Base URL	https://app-next-4qln1pg81-aragon-app.vercel.app
Suite	smoke
Playwright result	✅ passed
Summary	82 passed
HTML report	View report
GitHub job	✅ completed

View run #4884