This commit resolves an issue on iOS where TextCapitalization.words would incorrectly capitalize new text when it replaced a selected portion of an existing word.

Problem:

When using a TextFormField with textCapitalization: TextCapitalization.words, the following steps would lead to incorrect behavior:

1. Type a word, e.g., "Example".
2. Select a portion of the word that does not include the first letter, e.g., "ample".
3. Begin typing a replacement word, e.g., "pect".
4. The actual result would be "ExPect", with the first letter of the replacement text incorrectly capitalized.

Root Cause:

• The root cause was a behavioral discrepancy between a native UITextField and Flutter's custom FlutterTextInputView. On a native text field, the iOS keyboard observes selection changes and intelligently updates its capitalization state (e.g., switching to lowercase when a selection is adjusted away from a word boundary).
• However, the keyboard was not correctly reacting to these selection changes in Flutter's custom view, causing it to remain in an "uppercase" state after the initial selection. The automatic, declarative system of setting autocapitalizationType once was insufficient because the keyboard's internal observer logic was failing.

Solution:

This fix addresses the issue by taking manual control of the keyboard's capitalization state. The logic is now placed in setSelectedTextRangeLocal:, which acts as a reliable chokepoint for all selection changes, including typing, programmatic changes, and user-driven dragging of selection handles.

On each change, the code determines if the selection is at a word boundary, dynamically toggles the view's autocapitalizationType between Words and None, and then calls [self reloadInputViews] to reload the iOS keyboard to immediately discard its old state and reload its configuration based on the property we just changed.
This ensures that the keyboard's capitalization state is always in sync with the user's selection, correctly mimicking native behavior and resolving the bug.

Fixes #127922

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• [] I updated/added relevant documentation (doc comments with ///).
• [] I added new tests to check the change I am making, or this PR is test-exempt.
• [] I followed the breaking change policy and added Data Driven Fixes where supported.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

Note: The Flutter team is currently trialing the use of Gemini Code Assist for GitHub. Comments from the gemini-code-assist bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.