[iamnbutler]

Table cell edit (from 73's list). Builds on #86's table read.

desktop_set_cell takes pid, window, the scope snapshot, the table scope element, the row's element ID from a desktop_read table read, a column (exact title or 0-based index) and a value.

1. Reads the table with that snapshot and finds the cell's first editable control.
2. Writes the control:
   • a text field, text area or combo box goes through the type action. A web grid field takes feat: type into web text fields with key events so page scripts see the input #82's web route, so it must have keyboard focus, or it is refused with the click hint.
   • a checkbox, slider, stepper or date picker goes through set-value.
3. Reads the table again with the same snapshot. Peekaboo keeps a consumed snapshot readable ("Read-only snapshot inspection is still available").
4. Compares the cell at the same row position and column.
   • completed only when the control reads back the value and the row's other cells are unchanged.
   • Otherwise unknown, with cell.readback: differs, row_changed (for example, Finder re-sorting after a rename) or unreadable.

• A refused or unknown write keeps its outcome.

Refused before any input:

• cells with only text (such as Numbers and Excel, CELL_NOT_EDITABLE), with a hint pointing to a new recipe
• a control the snapshot didn't store (CELL_NOT_IN_SNAPSHOT)
• unknown, ambiguous or out-of-range columns
• an unknown row ID
• a boolean written to a text control

Code

• table.ts: the layout is factored out of buildTable, with no behavior change; the existing table tests pass. Adds locateCell.
• cell.ts: composes the reads and the action through injected IO, like notification actions.
• No native changes.

Docs

• tools.md: a row and a section for the new tool.
• New recipe "Edit a spreadsheet cell": click the cell, type with insert, press Return, then read again. Marked unverified.

Tests

• test/cell.test.mjs, against the Finder and Numbers fixtures plus a synthetic checkbox grid:
  • matched, differs, row_changed and unreadable readbacks
  • refused and unknown writes passed through
  • each pre-input refusal
  • the set-value route
• npm test: 38 pass. npm run check is clean.

Live checks: pending, screen locked. Finder rename, a web grid, and whether Numbers or Excel expose cell controls. I'll add these to #42.