Add braille text wrap modes with continuation marks

[LeonarddeR]

Link to issue number:

Part of #17010. Split out from #19916 at reviewer request — this is the second of three PRs. The pyphen abstraction layer was shipped in #20145; the syllable-aware wrap mode follows in a separate PR.

Summary of the issue:

The braille word-wrap setting is a single boolean that gives users no control over how words are broken at the display edge. When a word is cut mid-way there is also no visual indication that the word continues on the next row.

Description of user facing changes:

The boolean "word wrap" checkbox in the braille settings has been replaced with a Text wrap combo box with three choices:

• Off — Wrap at the raw edge of the display, cutting words in the middle if necessary. No visual indication that a word was cut.
• Show mark when words are cut — Wrap at the raw edge, but whenever a word is cut mid-way, replace the last cell of the row with a continuation mark (braille dots 7-8) so the reader knows the word continues on the next row.
• At word boundaries — Prefer breaking at spaces. If no space fits on the row, fall back to cutting the word and showing the continuation mark.

Existing user profiles with the old wordWrap = True / wordWrap = False setting are automatically upgraded: True becomes "At word boundaries" and False becomes "Off".

Description of developer facing changes:

• BrailleTextWrapFlag feature flag enum added to config.featureFlagEnums with members DEFAULT, NONE, MARK_WORD_CUTS, AT_WORD_BOUNDARIES.
• Config schema bumped v22 → v23; old wordWrap boolean is deprecated and bridged bidirectionally to textWrap via _linkDeprecatedValues, so add-ons reading or writing the old key keep working (with a deprecation warning).
• CONTINUATION_SHAPE = 0xC0 (dots 7-8) constant added to braille.

Description of development approach:

The continuation mark is unified: it consistently means "a word was cut here" regardless of mode, so readers get a predictable signal.

BrailleBuffer._calculateWindowRowBufferOffsets is extended to implement all three modes. BrailleBuffer._get_windowBrailleCells inserts the continuation mark into rows flagged in _continuationRows. BrailleBuffer._set_windowEndPos short-circuits space-seeking for NONE and MARK_WORD_CUTS modes (backwards scroll alignment).

Testing strategy:

Unit tests cover:

• All three wrap modes and their edge cases in _calculateWindowRowBufferOffsets (no cells, fits exactly, word cut, word too long for display, no space on line).
• Continuation-mark rendering in _get_windowBrailleCells.
• Profile upgrade from wordWrap = True/False → correct textWrap flag values.

Manual testing: loaded a pre-upgrade profile with wordWrap = True/False and confirmed the upgrade writes the expected textWrap value and the braille settings panel shows the matching label.

Known issues with pull request:

None.

Code Review Checklist:

• Documentation:
  • Change log entry
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English
• API is compatible with existing add-ons.
• Security precautions taken.