Use change.id as React key instead of array index

[Copilot]

Description

Array indices as React keys cause rendering issues when lists are reordered or modified. The DiffChange type includes an id field suitable for use as a stable key.

This PR updates the diff list components to use change.id as the React key instead of array indices, and replaces local Change interfaces with the proper DiffChange type from the domain layer for type safety.

Changes:

• Use change.id as key prop in PopulatedDiffList.tsx
• Replace local Change interface with DiffChange type in both PopulatedDiffList.tsx and DiffList.tsx
• Adopt base branch code style (no semicolons, no React imports)
• Merge latest refactoring changes from base branch

Before:

{changes.map((change, i) => (
  <DiffListItem
    key={i}
    path={change?.path}
    text={change?.text}
    ...
  />
))}

After:

{changes.map((change, i) => (
  <DiffListItem
    key={change.id}
    path={change?.path}
    text={change?.text}
    ...
  />
))}

Motivation and Context

Addresses code review feedback on PR #607: #607 (comment)

Using array indices as React keys is an anti-pattern that can cause rendering bugs when list items are reordered, added, or removed. The DiffChange schema already includes a unique id field that provides a stable key for each change item.

Screenshots (if appropriate):

N/A

Types of changes

• 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)

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[Copilot]

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

[ulrikandersen]

@copilot Resolve conflicts with base

[Copilot]

@copilot Resolve conflicts with base

Conflicts resolved in commit a76b31c. The changes now use change.id as the React key while adopting the base branch's code style (no semicolons).