Drop pivot slicer and timeline caches over a removed pivot (#1797)

CLAUDE.md

@@ -1828,6 +1828,27 @@
   (`model_edits_for`), so ones added after a table step follow its Undo/Redo;
   the step's recorded `model_edits` still restore its `#REF!` cases.
 
+## Pivot slicer and timeline caches on save (#1797)
+
+- `remove_pivot` notes the pivot as `(sheetId, name)` in
+  `SheetPackage::removed_pivots` (sheetId of its sheet's `<sheet>`, name from
+  its table part; either not found means nothing is noted), and `remove_sheet`
+  goes through it. The save runs `drop_pivot_slicers` right after
+  `drop_table_slicers`: a cache in `xl/slicerCaches` or `xl/timelineCaches`
+  whose `<pivotTables><pivotTable tabId name/>` entries are all noted goes with
+  its slicers or timelines (`SlicerKind`: `SLICERS`, `TIMELINES`; part, sheet
+  and workbook ext entries, `tle:timeslicer` anchors, relationship, defined
+  name), through the `drop_slicer_caches` shared with tables; a cache that
+  also filters a pivot that stays only loses the noted entries. A pivot added later under a
+  noted pair keeps it noted (its cache is its own). `remove_pivot` keeps the
+  cache part, override, workbook rel and `<pivotCache>` entry while another
+  pivot shares the cache. Synthetic fixtures only, as for
+  table slicers; restoring slicers on a sheet restore is not done.
+- The `Slicer_<name>` name of a dropped slicer cache stays in
+  `Workbook::defined_names` until a reload (the file is right on every save).
+  The suite's Go To leaves `Slicer_` and `NativeTimeline_` names whose formula
+  is `#N/A` out of its list (a user's own name over a range stays).
+
 ## Sheet hyperlinks in .xls, and file URI forms (#1726)
 
 - `gridcore/src/legacy/hlink.rs` is the HLINK record both ways: `body` for