fix: Prevent refreshViewport from reloading data from data provider

[vursen]

Description

DataCommunicator#refreshViewport used to set the same flag as reset(), which made the flush re-query the item count and re-fetch the viewport range from the data provider. Now it only regenerates and resends data for the items that are already active, matching the behavior of HierarchicalDataCommunicator#refreshViewport.

Changes:

• The former resendEntireRange flag is renamed to reloadViewportRange (it reloads the viewport range from the data provider and resends it).
• A new resendViewportRange flag drives the resend-only path used by refreshViewport: the active range is regenerated through the data generators and resent via update.set without any data provider queries, using the same wire format as before.
• If the viewport range changes in the same roundtrip, newly visible items are still fetched from the data provider as they were never loaded.

Type of change

• Bugfix
• Feature

Checklist

• I have read the contribution guide: https://vaadin.com/docs/latest/contributing/overview
• I have added a description following the guideline.
• The issue is created in the corresponding repository and I have referenced it.
• I have added tests to ensure my change is effective and works as intended.
• New and existing tests are passing.
• I have performed self-review and corrected misspellings.

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

Test Results

 1 456 files  ±0   1 456 suites  ±0   1h 26m 55s ⏱️ - 5m 5s
10 303 tests +2  10 235 ✅ +2  68 💤 ±0  0 ❌ ±0 
10 775 runs  +2  10 706 ✅ +2  69 💤 ±0  0 ❌ ±0 

Results for commit d5d10c0. ± Comparison against base commit 9977f32.

[tltv]

LGTM, one case to think about with Grid is how Column.setPartNameGenerator or Column.setTooltipGenerator are affected. Looks like it could now require additional DataProvider.refreshAll() to keep it function exactly same as before. But considering how JavaDoc never said refreshViewport() to reload data, approving.

[tltv]

For reference regarding last review comment: Grid.Column.setPartNameGenerator calls refreshViewport().

[vursen]

For reference regarding last review comment: Grid.Column.setPartNameGenerator calls refreshViewport().

Yes, that's actually the expected behavior. Part name and tooltip generation shouldn't trigger another data provider call if the data is already there.