[MrAshRhodes]

Summary

Scrolling capture could return only the first viewport: pressing Done right after a small scroll, before the page settled, dropped that last viewport. Capture also relied on the user scrolling at a pace the engine could follow, with no feedback.

• Fix: Done now drains the in-flight step and the final small movement. An uncertain final join pauses for review instead of returning a truncated image. Undo no longer re-adds the final frame unless the content moved.
• Automatic scrolling (default on): scrolls the original window in small overlapping steps (20% of the content height, 0.25s settle, 2s response timeout), capturing each step before advancing. It stops after 200 steps / 2 minutes or 3 unchanged steps and pauses for review instead of assuming the bottom. Any pause drops back to manual, so Resume continues manually. It posts events only to the captured window and needs Accessibility; denial or any source/target failure falls back to manual with a message pointing at Privacy & Security → Accessibility.
• Preference: Preferences → Capture → Automatically scroll during scrolling capture (glint.scrollCaptureAutoScroll, default on, restored by Reset). Turning it off scrolls manually without requesting the extra permission and shows a pace indicator: Too fast — slow down to keep frames aligned., Steady — keep this pace., Too slow — scroll down a little, or choose Done if finished.
• Docs / release: README, guide, docs/CORE_API.md, the CONTRIBUTING manual checklist and the changelog are updated, and the version is bumped to 1.9.1 with make prepare-release VERSION=1.9.1.

Issue

Fixes #132

Verification

• Scripts/swiftw.sh test --no-parallel — passed: Test run with 1504 tests in 137 suites.
• Scripts/swiftw.sh test --no-parallel --filter 'ScrollCapture|ScrollStitcher|ScrollGrabPolicy|ExportAndPrefsTests/(scrollingCaptureDefaultsToAutomaticAndPersistsManualMode|resetRestoresAutomaticScrollingCapture)|ScrollingCapturePipelineTests' — passed: 52 tests in 8 suites, including the new regression finishingCapturesTheFinalSmallScrollBeforeItSettles, Done during a delayed scroll, manual pace, target loss, denied permission, source failure, safety limit, unsettled/bad join and undo cases (all against fake scroll sources).
• make prepare-release VERSION=1.9.1, node .github/scripts/changelog.cjs check and node --test .github/scripts/site.test.cjs .github/scripts/changelog.test.cjs — passed (32 tests).
• make app — built dist/Glint.app 1.9.1 (92), ad-hoc signed locally; the release workflow produces the Developer ID signed and notarized artifacts from the tag.
• git diff --check — clean.

Manual gap: real desktop scrolling (event delivery to a live window, the Accessibility prompt and the on-screen HUD colors) was not exercised in this environment; the scroll driver and permission paths are covered by fakes only. The CONTRIBUTING manual checklist covers it.