Add path-filtered repository history

TESTING.md

@@ -207,6 +207,11 @@ xcrun simctl launch booted de.rfc1437.gotcha
 - [ ] In Files, traverse several nested folders using rows, the navigation-bar
       Back button, and the left-edge swipe. Folder contents and titles match the
       repository hierarchy.
+- [ ] In the repository root and in several nested folders, switch between
+      **Files** and **History**. Each folder history contains only commits that
+      affect that folder or its descendants. Switch back to Files and verify the
+      same folder and navigation stack are preserved. Open a history commit and
+      verify its changed-files detail opens normally.
 - [ ] Open representative source files in several languages, including Rust,
       Swift, and a scripting or markup language. Keywords, strings, comments,
       types, and punctuation use plausible language-specific highlighting.
@@ -223,6 +228,11 @@ xcrun simctl launch booted de.rfc1437.gotcha
       is syntax-highlighted, selectable, does not word-wrap, and scrolls
       horizontally for long lines. Switch back and verify the rendered preview
       is restored without stale or overlapping content.
+- [ ] Switch Markdown files among **Preview**, **Source**, and **History** and
+      switch other source and native-preview files between **Content** and
+      **History**. Each history contains only commits that affect that exact
+      file. Returning to content preserves the file path and restores its native
+      preview or source presentation without stale or overlapping views.
 - [ ] Open representative image, PDF, audio, and video files. Each uses the
       native preview appropriate to its media type and returns cleanly to Files.