Follow-up: fix reconfigure class migration edge cases

[VishnuSivadasVS]

Motivation

• Reconfiguration after changing classNames left stale classes/selectors in the DOM and could produce duplicate toggle buttons or mis-targeted control cells.
• Multi-row <thead> support needed consistent application of visibility and removal of only injected control cells.
• Inline review flagged accidental insertion of control cells into generated details rows and duplicate delegated listeners across remounts.

Description

• Add swapClassTokens(...) and _migrateStructureClasses(prevOptions, nextOptions) to migrate existing DOM classes for control/toggle/details elements when structural classNames change.
• Avoid inserting control <td> into details rows by skipping rows with the details class in _ensureControlColumn() and track injected header <th> per header row with _insertedHeaderControls (a WeakSet) so destroy() removes only injected header controls.
• Ensure event delegation handlers are only attached once per controller by guarding _clickHandler and _keyHandler, apply visibility to all header rows via headerRows, and add a _reconfigure(nextOptions, structural) path that uses isStructuralOptionsChange(...) to detect structural changes.
• Rebuilt distribution artifacts and updated README/docs to reflect multi-row <thead> support and the above fixes.

Testing

• Ran npm run build which completed successfully and produced updated dist/* artifacts.
• Launched a lightweight docs server with python3 -m http.server 4173 and captured a browser render with a Playwright script to validate the docs page loaded after the build, which succeeded.
• Performed automated code searches/inspections to verify the new helpers and reconfigure path exist in src/CollapseTable.js and the built bundles include the same changes.

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[chatgpt-codex-connector]

Toggle control-column visibility on all header rows

This block now injects a control <th> into every THEAD row, but _updateTogglesVisibility() still only toggles this.headerRow.cells[0]. In multi-row headers when no data columns are hidden, secondary header rows keep a visible control cell while body control cells are hidden, leaving an orphan leading column and inconsistent header/body alignment.

Useful? React with 👍 / 👎.

[chatgpt-codex-connector]

Track body insertions before deleting first data cells

Setting _insertedControl when only a header row receives an injected control cell makes destroy() remove the first cell from every data row even if those body cells were never injected by CollapseTable. In multi-row tables where only some header rows needed a synthesized control <th>, calling unset() can delete user-authored first-column data.

Useful? React with 👍 / 👎.