Fix invalid selection/span ranges causing editor crashes

[Twinsen81]

DODROID-621

Prevents crashes caused by invalid selection offsets and invalid span ranges during text mutations (e.g., outdent/indent, span restoration), which can surface as SpannableStringBuilder/selection handle failures on newer Android builds.

The crash recording:
https://github.com/user-attachments/assets/f32a42c5-fdf2-4db3-a55f-19c0b6494587

Changes:

• Clamp AztecText.setSelection(...) to a valid range (also avoiding the end-of-buffer marker).
• Guard/clamp span restoration ranges in SuggestionWatcher and LineBlockFormatter to avoid setSpan crashes on edge cases.
• Add a regression test reproducing the “outdent at start of document” crash.

Testing Steps

• Run the demo app
• Long-click -> Select all -> Cut
• Ensure the cursor is at the first line at position 0
• Tap the Indent button on the toolbar
• Enter some text
• Move the cursor back to position 0
• Tap the Outdent button
• Verify the app doesn't crash
• Smoke-test the editor in the demo app, especially the indentation

The crashes

Exception java.lang.IndexOutOfBoundsException: setSpan (-1 ... -1) starts before 0
  at android.text.SpannableStringBuilder.checkRange (SpannableStringBuilder.java:1341)
  at android.text.SpannableStringBuilder.setSpan (SpannableStringBuilder.java:695)
  at android.text.SpannableStringBuilder.setSpan (SpannableStringBuilder.java:687)
  at androidx.emoji2.text.SpannableBuilder.setSpan (SpannableBuilder.java:135)
  at android.text.Selection.setSelection (Selection.java:94)
  at android.text.Selection.setSelection (Selection.java:78)
  at android.widget.EditText.setSelection (EditText.java:147)
  at org.wordpress.aztec.formatting.IndentFormatter.outdent (IndentFormatter.kt:111)
  at org.wordpress.aztec.formatting.BlockFormatter.outdent (BlockFormatter.kt:80)
  at org.wordpress.aztec.AztecText.outdent (AztecText.kt:1217)
  at org.wordpress.aztec.toolbar.AztecToolbar.onToolbarAction (AztecToolbar.kt:659)
  at org.wordpress.aztec.toolbar.AztecToolbar.setupToolbarItems$lambda$18$lambda$17 (AztecToolbar.kt:799)

Exception java.lang.RuntimeException:
  at android.text.SpannableStringBuilder.setSpan (SpannableStringBuilder.java:694)
  at android.text.SpannableStringBuilder.setSpan (SpannableStringBuilder.java:677)
  at androidx.emoji2.text.SpannableBuilder.setSpan (SpannableBuilder.java:135)
  at org.wordpress.aztec.formatting.LineBlockFormatter.applyWithRemovedSpans (LineBlockFormatter.kt:222)
  at org.wordpress.aztec.formatting.LineBlockFormatter.insertSpanAfterBlock (LineBlockFormatter.kt:201)
  at org.wordpress.aztec.formatting.LineBlockFormatter.applyHorizontalRule (LineBlockFormatter.kt:121)
  at org.wordpress.aztec.AztecText.toggleFormatting (AztecText.kt:1459)
  at org.wordpress.aztec.toolbar.AztecToolbar.onToolbarAction (AztecToolbar.kt:615)
  at org.wordpress.aztec.toolbar.AztecToolbar.setupToolbarItems$lambda$18$lambda$17 (AztecToolbar.kt:799)
  at android.view.View.performClick (View.java:8464)

Exception java.lang.IllegalArgumentException: Invalid offset: 3. Valid range is [0, 2]
  at android.text.method.WordIterator.checkOffsetIsValid (WordIterator.java:401)
  at android.text.method.WordIterator.isBoundary (WordIterator.java:112)
  at android.widget.Editor$SelectionHandleView.positionAtCursorOffset (Editor.java:7941)
  at android.widget.Editor$HandleView.updatePosition (Editor.java:6297)
  at android.widget.Editor$HandleView.updateDrawable (Editor.java:6052)
  at android.widget.Editor$SelectionHandleView.updateSelection (Editor.java:7708)
  at android.widget.Editor$HandleView.positionAtCursorOffset (Editor.java:6257)
  at android.widget.Editor$SelectionHandleView.positionAtCursorOffset (Editor.java:7940)
  at android.widget.Editor$HandleView.invalidate (Editor.java:6122)
  at android.widget.Editor$SelectionModifierCursorController.invalidateHandles (Editor.java:8981)
  at android.widget.Editor.invalidateHandlesAndActionMode (Editor.java:2595)
  at android.widget.TextView.spanChange (TextView.java:13810)
  at android.widget.TextView$ChangeWatcher.onSpanChanged (TextView.java:17629)
  at android.text.SpannableStringBuilder.sendSpanChanged (SpannableStringBuilder.java:1309)
  at android.text.SpannableStringBuilder.setSpan (SpannableStringBuilder.java:754)
  at android.text.SpannableStringBuilder.setSpan (SpannableStringBuilder.java:678)
  at androidx.emoji2.text.SpannableBuilder.setSpan (SpannableBuilder.java:135)
  at org.wordpress.aztec.watchers.SuggestionWatcher.reapplyCarriedOverInlineSpans (SuggestionWatcher.kt:147)
  at org.wordpress.aztec.watchers.SuggestionWatcher.onTextChanged (SuggestionWatcher.kt:82)
  at android.widget.TextView.sendOnTextChanged (TextView.java:13573)
  at android.widget.TextView.handleTextChanged (TextView.java:13702)
  at android.widget.TextView$ChangeWatcher.onTextChanged (TextView.java:17605)
  at android.text.SpannableStringBuilder.sendTextChanged (SpannableStringBuilder.java:1269)
  at android.text.SpannableStringBuilder.replace (SpannableStringBuilder.java:578)
  at androidx.emoji2.text.SpannableBuilder.replace (SpannableBuilder.java:308)
  at android.text.SpannableStringBuilder.append (SpannableStringBuilder.java:272)
  at androidx.emoji2.text.SpannableBuilder.append (SpannableBuilder.java:337)
  at androidx.emoji2.text.SpannableBuilder.append (SpannableBuilder.java:48)
  at org.wordpress.aztec.formatting.LineBlockFormatter$insertSpanAfterBlock$3.invoke (LineBlockFormatter.kt:202)
  at org.wordpress.aztec.formatting.LineBlockFormatter$insertSpanAfterBlock$3.invoke (LineBlockFormatter.kt:201)
  at org.wordpress.aztec.formatting.LineBlockFormatter.applyWithRemovedSpans (LineBlockFormatter.kt:220)
  at org.wordpress.aztec.formatting.LineBlockFormatter.insertSpanAfterBlock (LineBlockFormatter.kt:201)
  at org.wordpress.aztec.formatting.LineBlockFormatter.applyHorizontalRule (LineBlockFormatter.kt:121)
  at org.wordpress.aztec.AztecText.toggleFormatting (AztecText.kt:1459)
  at org.wordpress.aztec.toolbar.AztecToolbar.onToolbarAction (AztecToolbar.kt:615)
  at org.wordpress.aztec.toolbar.AztecToolbar.setupToolbarItems$lambda$18$lambda$17 (AztecToolbar.kt:799)
  at android.view.View.performClick (View.java:8508)

Exception java.lang.IllegalArgumentException:
  at android.text.method.WordIterator.checkOffsetIsValid (WordIterator.java:384)
  at android.text.method.WordIterator.isBoundary (WordIterator.java:94)
  at android.widget.Editor$SelectionHandleView.positionAtCursorOffset (Editor.java:5470)
  at android.widget.Editor$HandleView.invalidate (Editor.java:4580)
  at android.widget.Editor$SelectionModifierCursorController.invalidateHandles (Editor.java:6151)
  at android.widget.Editor.invalidateHandlesAndActionMode (Editor.java:1985)
  at android.widget.TextView.spanChange (TextView.java:9941)
  at android.widget.TextView$ChangeWatcher.onSpanAdded (TextView.java:12570)
  at android.text.SpannableStringBuilder.sendSpanAdded (SpannableStringBuilder.java:1283)
  at android.text.SpannableStringBuilder.setSpan (SpannableStringBuilder.java:775)
  at android.text.SpannableStringBuilder.setSpan (SpannableStringBuilder.java:674)
  at androidx.emoji2.text.SpannableBuilder.setSpan (SpannableBuilder.java:135)
  at org.wordpress.aztec.watchers.SuggestionWatcher.reapplyCarriedOverInlineSpans (SuggestionWatcher.kt:147)
  at org.wordpress.aztec.watchers.SuggestionWatcher.onTextChanged (SuggestionWatcher.kt:82)
  at android.widget.TextView.sendOnTextChanged (TextView.java:9769)
  at android.widget.TextView.handleTextChanged (TextView.java:9866)
  at android.widget.TextView$ChangeWatcher.onTextChanged (TextView.java:12538)
  at android.text.SpannableStringBuilder.sendTextChanged (SpannableStringBuilder.java:1263)
  at android.text.SpannableStringBuilder.replace (SpannableStringBuilder.java:575)
  at androidx.emoji2.text.SpannableBuilder.replace (SpannableBuilder.java:308)
  at android.text.SpannableStringBuilder.insert (SpannableStringBuilder.java:224)
  at androidx.emoji2.text.SpannableBuilder.insert (SpannableBuilder.java:316)
  at androidx.emoji2.text.SpannableBuilder.insert (SpannableBuilder.java:48)
  at org.wordpress.aztec.formatting.IndentFormatter.indent (IndentFormatter.kt:49)
  at org.wordpress.aztec.formatting.BlockFormatter.indent (BlockFormatter.kt:75)
  at org.wordpress.aztec.AztecText.indent (AztecText.kt:1211)
  at org.wordpress.aztec.toolbar.AztecToolbar.onToolbarAction (AztecToolbar.kt:655)
  at org.wordpress.aztec.toolbar.AztecToolbar.setupToolbarItems$lambda$18$lambda$17 (AztecToolbar.kt:799)
  at android.view.View.performClick (View.java:6614)

[zwarm]

@Twinsen81 . LGTM! I really like the clamping at the AztecText level and the defensive guards in the formatters should prevent the SpannableStringBuilder crashes. Nice work!