fix(datagrid): route Cmd+V to row paste when clipboard holds copied rows

[datlechin]

Summary

Fixes a Cmd+C / Cmd+V asymmetry: Cmd+C copies the selected rows (row-level), but Cmd+V was always cell-pasting whenever a cell had focus — so copying a row then pasting silently overwrote the row's tail columns with the source row's leading values instead of inserting a new row.

Root cause

KeyHandlingTableView.paste(_:) chose between cell paste and row paste based purely on whether a cell was focused:

if focusedRow >= 0, focusedColumn >= 1 {
    pasteCellsFromClipboard(...)
} else {
    dataGridPasteRows()
}

Clicking any cell sets focus, but copy(_:) always uses selectedRowIndexes. Net effect: copy works at row level, paste at cell level, and the round trip mangles cells.

Fix

pasteCellsFromClipboard now defers to row paste on two signals:

1. Pasteboard tag: ClipboardProvider gains writeRows(tsv:html:?) which writes the TSV (and optional HTML) plus a com.TablePro.gridRows pasteboard type. hasGridRows reads it. Migrates RowOperationsManager.copySelectedRowsToClipboard and TableViewCoordinator.copyRows / copyRowsWithHeaders to use it. Drops the now-unused writeTabular.
2. Shape heuristic: if every line of the clipboard TSV has exactly numberOfDataColumns values, treat it as full rows. Catches external row-shaped data (e.g., from another DB tool) that the user clearly meant as an insert.

Cell paste continues to work for shape-mismatched TSV (external spreadsheet selections, single-column copies, etc.).

Audit of other paste paths (no changes needed)

• TableRowViewWithMenu right-click row > Paste → already calls dataGridPasteRows directly
• MainContentCommandActions.pasteRows (menu / .pasteRows notification) → already calls coordinator?.pasteRows() directly

Only the Cmd+V keyboard path needed routing fix.

Test plan

• Build clean
• RowOperationsManagerCopyTests pass (mock updated to new protocol)
• Manual: Cmd+C on row, Cmd+V → inserts new row ✓
• Manual: Cmd+C on multiple rows, Cmd+V → inserts N rows ✓
• Manual: Cmd+C on single cell, Cmd+V into another cell → cell paste ✓
• Manual: paste TSV from external (Excel) into cell selection → cell paste ✓
• Manual: right-click row > Paste → inserts (unchanged) ✓

[chatgpt-codex-connector]

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