m hit two bugs opening the Slice 1 export in Excel / Windows:
1. **Excel showed a "Repairs required" prompt** on open. Root cause:
the SetPanes call passed only `{Freeze: true, YSplit: 1}` — the
obvious-but-wrong shape. The resulting <pane> XML missed the
`topLeftCell` and `activePane` attributes that Excel requires for
a frozen-row pane (excelize's parser is permissive on re-read but
Excel is strict). Fix: complete the Panes struct (TopLeftCell="A2",
ActivePane="bottomLeft", Selection on bottomLeft) and surface
SetPanes errors instead of `_ =`-ignoring them.
2. **Windows Explorer / Excel's File→Info showed Modified=2006-09-16
("xuri")** — excelize's hardcoded first-commit defaults. Root cause:
buildXLSX never called SetDocProps so the canned defaults leaked.
Fix: SetDocProps({Created, Modified} = meta.GeneratedAt;
Creator = "Paliad (<firm>)"; Title/Description scoped per export).
3. **Bonus**: the outer-zip entry mtimes were stamped 2000-01-01 (the
deterministic constant) so extracted files showed a Y2K Modified
date in Explorer. Now stamped meta.GeneratedAt, which preserves
determinism within an export (same row state + same GeneratedAt →
same bytes, the actual m's-Q6 contract).
Also: set the active sheet to __meta (index 0) after sheet creation so
a future code path that adds/removes sheets can't leave an out-of-range
active-sheet index that would trip a separate "repairs required" path.
Regression tests in dump_export_test.go pin all three fixes by re-opening
the generated xlsx via excelize.OpenReader and asserting:
- docProps Created/Modified == meta.GeneratedAt (RFC 3339 UTC)
- docProps Creator contains "Paliad"
- xlsx bytes never contain "2006-09-16T00:00:00Z" or "<dc:creator>xuri</dc:creator>"
- sheet2/sheet3 raw XML carries topLeftCell + activePane + state=frozen
- outer-zip entries' Modified is within ±2s of GeneratedAt
- developer hatch: DUMP_EXPORT=1 writes /tmp/paliad-export-debug.{zip,xlsx}
for opening in real Excel.
