fix(datagrid): cell/selection copy, persist hidden columns & filters, JSON popover

[J2TeamNNL]

Summary

• Context menu Copy copies the clicked cell value, or the rectangular grid selection when one exists, matching Cmd+C. The row-number column copies the full row. Copy As keeps Rows, With Headers, JSON, CSV, Markdown, and the SQL variants.
• Hidden columns persist when you change them and are restored before the first load, so reopening a table keeps them hidden and the query omits them instead of running SELECT *.
• Applied filters persist on Apply, so reopening a table restores the last filter.
• Filter bar visibility follows the Panel State setting: Always Hide stays closed, Always Show stays open, Restore Last shows the bar only when a saved filter exists.
• JSON detail popover shows long string values up to 300 characters in the tree view (raw value unchanged).

Test plan

• Right-click a cell → Copy → pastes the cell value (blob → 0x…, NULL → NULL)
• Select a range of cells → right-click → Copy → pastes the selection (matches Cmd+C)
• Right-click the row-number column → Copy → pastes the full row
• Copy As → Rows / With Headers still work
• Hide a column, close the tab, reopen the table → column stays hidden and the query omits it
• Apply a filter, close the tab, reopen → filter restored (Restore Last)
• Panel State Always Hide → table opens with the filter bar closed
• Panel State Restore Last with no saved filter → filter bar stays closed
• Panel State Always Show → filter bar open even with no filter
• Open a row with a long JSON string → popover shows up to 300 chars, copy gives the full value

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve row-copy fallback from row-number menu

When the context menu is opened from the row-number/non-data column on the currently focused row, representedObject is nil, so this fallback reuses the focused data column and Copy copies that cell instead of the full row. This breaks the advertised row-header fallback path; the focused-cell fallback needs to be gated so a click that resolved to a non-data column still dispatches row copy.

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[datlechin]

Pushed review fixes (commits 15d0198a, ac29ba8b):

• Persistence: hidden columns and applied filters now persist on change, so reopening a table restores the hidden-column set (no more SELECT *) and the last applied filter. Previously these only saved on tab switch, so closing without switching lost them. Regression tests added.
• Filter bar default: the three Panel States are now distinct, resolved in one place (FilterCoordinator.resolvedRestoredState). Restore Last shows the bar only when a saved filter exists, instead of popping an empty bar on every table open. Reverted the docs/CHANGELOG line that described the old behavior.
• Copy menu: removed the redundant Copy As → Cell Value (top-level Copy already copies the cell). Context-menu Copy now honors a rectangular grid selection, matching Cmd+C.
• Deduped the column-scoping query rebuild and removed dead code.

Build and swiftlint --strict clean; affected suites pass.

Note: this branch is behind main (CHANGELOG entries sit under [0.46.0]). Rebase onto main before merge so they move to [Unreleased].