[simonbs]

The line-number gutter can remain sharp above a navigation scroll-edge blur because each layout pass brings it in front of every scroll-view subview. The existing workaround depends on finding a private _UIScrollPocket view, which no longer matches the current UIKit hierarchy.

Place the gutter immediately above the text input view so it still covers text and selection content while preserving overlays above both. Remove the private-class lookup and its cached view.

Validation:

• All 161 package tests pass on an iPhone 17 Pro simulator running iOS 27.2, with no build warnings.
• The overlay-ordering regression fails against the previous implementation and passes with this change. Tests also cover line-number visibility changes and horizontal gutter pinning.
• Verified the standard soft navigation scroll-edge effect in light and dark appearance on iOS 27.2, without custom blur views or layer-position overrides.
• Built and ran the bundled Example app and Runestone Editor 1.6.2 against this revision on iOS 27.2. Checked light/dark rendering, vertical and horizontal gutter scrolling, selection handles, caret rendering, typing, and native undo. The Example also passed line-number visibility toggling. Runestone Editor used a disposable scratch document with line numbers enabled through public view settings in the debugger; its existing header blur and entitlement code were unchanged.
• GitHub build/test and example-project jobs pass on Xcode 15.2 and 16.2; documentation and SwiftLint jobs pass.
• Strict SwiftLint passes for both changed files. Full-repository lint reports five existing prefer_self_in_static_references violations in unchanged files.
• An iOS 26 runtime was not available locally.

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