Replace map with repeat directive for rows rendering

[dcharles525]

This allows table updates without resetting any elements in the context of the row, like a kabob menu.

Summary

When rows data updates (e.g. from a polling interval), Lit's .map() destroys and recreates all row
DOM nodes on every render cycle. Any stateful child element inside a row, such as an open
trailhand-action-menu loses its state because the element is replaced with a new instance.

Replacing .map() with Lit's repeat() directive keys each row to row[this.keyField] (defaults to
'id'). Lit reuses existing DOM nodes for rows whose key hasn't changed, only creating/destroying nodes
for rows that are genuinely added or removed. Stateful child elements survive data refreshes.

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Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ⚡ Performance improvement

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Changes Made

Primary Changes

• Replace .map() with repeat() directive in the row rendering section of DataTable.render()
• Add import { repeat } from 'lit/directives/repeat.js'

Secondary/Collateral Changes

• None

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Technical Notes

Components:

• src/components/data-table/data-table.ts row rendering changed from .map() to
  repeat(this._paginatedRows, (row) => row[this.keyField], (row) => html\...`)`

Implementation Details

Lit's .map() treats every re-render as a full replacement with no concept of row identity. repeat()
accepts a key function as its second argument and uses it to match old nodes to new data. When the key
is stable (same row ID), the existing <tr> and all its children are updated in place rather than
recreated.

The key function uses row[this.keyField], the existing public keyField property (default: 'id',
configurable via the key-field attribute). No new API surface introduced.

lit/directives/repeat.js is part of the lit package already present as a dependency, no new
packages added.

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Testing

How to Test

1. Render a trailhand-table with a renderActions prop that returns a trailhand-action-menu
2. Open an action menu on any row
3. Trigger a data refresh by updating the rows prop with the same rows (simulating a poll)
4. Expected: the action menu remains open; the row is not recreated

Test Coverage

• Unit tests added/updated
• Integration tests added/updated
• E2E tests added/updated
• Manual testing completed

Browsers Tested

• Chrome
• Firefox
• Safari
• Edge

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Potential Regressions

• Row rendering in all table instances, verify rows still render correctly with sorting, filtering, and
  pagination active
• Any consumer passing a key-field attribute should verify their key values are unique per row

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Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code in hard-to-understand areas
• I have updated documentation as needed
• My changes generate no new warnings or errors
• I have tested my changes locally
• Any dependent changes have been merged and published

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Additional Context

This fix was identified while integrating trailhand-table into a polling-driven application list view.
The table receives fresh rows data every 30 seconds. Without repeat(), every poll cycle caused all
open action menus to close because their DOM nodes were destroyed. The repeat() directive resolves
this by preserving node identity across renders.

[Hannahbird]

LGTM