Formulas: Trace Error draws arrows back to the cell an error starts in

New query command formulas.traceError and a Trace Error item in the
Error Checking menu, between Error Checking… and Circular References.
From the cell it follows the first reference that shows the same error
(in a range, its first cell showing it) to the cell the error starts in,
as measured in Excel, and returns that source and the arrows: links
between the error cells, and arrows from the source's own references.
The walk visits each cell once and stops after 10,000 links.

The grid's trace now holds arrows with the sheets of both ends, built
once from the command's result. Error links are drawn in a new red sheet
token, the other arrows in a token for the blue they had. "Trace Error"
is translated in all 18 catalogs (German: Spur zum Fehler).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SAgnkqJiy3v24Hp25dQLRj

docs/ui-parity.md

@@ -1,6 +1,6 @@
 # UI parity
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-11-01 · **Change:** minor (trace arrows stay through a zoom (#3097); earlier: Formulas › Function Library as labelled buttons with category menus; Recently Used and the Insert Function categories; Esc leaves a File-page text field before closing the view; earlier: checkbox cells print as boxes; Ctrl+arrow and Ctrl+Shift+arrow while pointing a formula reference; editing a hyperlink loads its existing fields; AutoSum over a selected row puts its total to the right; ribbon catalog count 276 / 292) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
+> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-11-01 · **Change:** minor (Formulas › Error Checking › Trace Error; trace arrows stay through a zoom (#3097); earlier: Formulas › Function Library as labelled buttons with category menus; Recently Used and the Insert Function categories; Esc leaves a File-page text field before closing the view; earlier: checkbox cells print as boxes; Ctrl+arrow and Ctrl+Shift+arrow while pointing a formula reference; editing a hyperlink loads its existing fields; AutoSum over a selected row puts its total to the right; ribbon catalog count 276 / 292) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
 
 Interaction, controls and feel, against Excel. Part of [target-app-parity.md](target-app-parity.md).
 **UI/UX fidelity: ~55% ready, 50–80 h** (estimated). Ribbon command coverage is measured
@@ -25,7 +25,7 @@ Sources: `crates/ui-egui/src` (ribbon, grid, editor, formula bar, dialogs, panes
 | Formula bar with Name Box, expand, function hints | yes | yes; grows with its content from one to five lines (Alt+Enter, wrapped text, or viewing a multi-line cell), then scrolls with the caret in view, the Name Box and buttons staying on the first line; the chevron pins it at five; the in-cell editor shows every line | done; no drag-to-resize handle |
 | Sheet tabs: rename, reorder, colour, hide, scroll | yes | yes | Ctrl-drag (Cmd or Option on macOS) drops a copy (#971); active tab revealed on navigation and resize (#681); manual wheel/trackpad browsing preserved; rename focus bug on macOS (#145) |
 | Formula bar with Name Box, expand, function hints | yes | yes | done; dynamic-array spill children show the source formula muted and read-only, using current spill ownership |
-| Formulas › Error Checking arrow: Circular References | yes | yes: the button opens Error Checking and its arrow opens a menu with Error Checking… and Circular References, which lists a cell on each circular reference as `Sheet!A1`, up to 100, and selects the one picked, on its own sheet (unavailable when there are none) | done; the Error Checking… item and the limit of 100 are GridCraft's own |
+| Formulas › Error Checking arrow: Trace Error, Circular References | yes | yes: the button opens Error Checking and its arrow opens a menu with Error Checking…, Trace Error and Circular References. Trace Error (`formulas.traceError`, 11-01) follows the active cell's error back through the first reference showing the same error (in a range, its first cell showing it) to the cell it starts in, and draws red arrows along the way and blue ones from that cell's own references, as measured in Excel; on a cell without an error it draws nothing and the arrows shown stay. Circular References lists a cell on each circular reference as `Sheet!A1`, up to 100, and selects the one picked, on its own sheet (unavailable when there are none) | done; the Error Checking… item and the limit of 100 are GridCraft's own; a new trace replaces the arrows shown, where Excel adds to them, and there is no Remove Precedent Arrows |
 | Sheet tabs: rename, reorder, colour, hide, scroll | yes | yes | active tab revealed on navigation and resize (#681); manual wheel/trackpad browsing preserved; rename focus bug on macOS (#145) |
 | Sheet tabs: rename, reorder, colour, hide, scroll | yes | yes | active tab revealed on navigation and resize (#681); New sheet (+) right after the last tab, the strip capped at 60% of the bar (#943); manual wheel/trackpad browsing preserved; next/previous skips Hidden and VeryHidden sheets and retains the current sheet and selection when no visible destination exists; rename focus bug on macOS (#145) |
 | Status bar: Sum/Count/Average and more, view buttons, zoom | yes | yes; a right-click on the status bar opens a menu that turns the statistics on and off (Average, Count, Numerical Count, Minimum, Maximum, Sum; `view.statusBar`) | done for the statistics; the other status bar options are not customizable |
@@ -196,6 +196,7 @@ scrollbar bugs 2–4 · pixel/feel pass against observed Excel 7–12.
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-11-01 | minor | Formulas › Error Checking › Trace Error (`formulas.traceError`): red arrows from the cell an error starts in to the selected cell, through the first reference showing the same error at each step, and blue arrows from that cell's own references, as measured in Excel; the command returns the source and the arrows |
 | 2026-11-01 | minor | Trace arrows stay when the sheet is zoomed (View › Zoom, the status bar, Ctrl+wheel), as in Excel; every zoom used to remove them (#3097) |
 | 2026-10-31 | minor | Esc in a File-page text field leaves the field and cancels editing; the next Esc returns to the sheet (#3035) |
 | 2026-10-31 | minor | Recently Used lists the functions most recently entered in a formula from any source, kept with the preferences; the Insert Function dialog is titled as in Excel, its category list (Most Recently Used, All, each category) works, and its category column follows the widest name shown |