M7: preserve overlapping text when dragging paragraphs (#594) (#1052)

* M7 #594: preserve ordinary paragraph drags (source-only GGEO candidate) [skip ci]

Route body drags through source-preserving MoveObjects, bind gestures to
the document generation, and keep added-content input ownership with
the Edit panel open or closed. Add nine real-shell source regressions.

Source-only transfer to the owner's fork, explicitly authorized before
validation. Independently source-reviewed; formatting, builds, tests,
rendering and all gates remain pending on ggeo-ai02. No upstream PR.

AI-assisted with OpenAI.

* M7 #594: record validated ordinary paragraph drags

Format the source-reviewed candidate and record successful GGEO validation:
focused UI/engine tests, exact-base source loss, native drag/history/save/reopen,
independent Poppler checks, and all eight repository CI gates.

Credit: @FredApps

* M7: use generic validation wording

* Tests: pin the clock where two saves or combines are compared byte for byte

Co-Authored-By: Claude Opus 5.5 <[email protected]>

---------

Co-authored-by: FredApps <[email protected]>
Co-authored-by: Brandon Thomas <[email protected]>
Co-authored-by: Claude Opus 5.5 <[email protected]>

crates/engine/src/tests.rs

@@ -525,7 +525,8 @@ fn create_multiple_reads_each_source_only_after_the_previous_one_is_released() {
 
 #[test]
 fn create_multiple_gives_the_bytes_of_combine_ranges_and_refuses_a_bad_source() {
-    let s = Session::new();
+    // The two combines are compared byte for byte, and each stamps the clock: pin it.
+    let s = Session::new().with_clock(|| 1_700_000_000);
     let (a, b) = (Arc::new(fixture(3)), Arc::new(fixture(2)));
     let sources: Vec<CombineSource> =
         vec![("a".into(), a.clone(), Some("1-2".into())), ("b".into(), b, None), ("a".into(), a.clone(), Some("3".into()))];