[nagisml]

Lua macros: visual form designer (#982)

@AgreeDK ⚠️ Depends on #. Merge that one first.
This branch builds on feature/982-lua-ui-forms (macro UI functions and opensak.form{}). Until that PR is merged, this PR's diff also shows its commits.

Part of #938 / #982. The form designer was split off from the UI-functions PR so the runtime API could be reviewed on its own.

What it does

Tools → Form designer… (Ctrl+Shift+D) in the macro window builds opensak.form{} dialogs with the mouse:

• Edits forms in place. If the cursor is inside an opensak.form{…} table, the designer opens that form and Update macro writes it back. Otherwise Insert into macro puts a new form at the cursor, indented to match.
• Doesn't run the macro. The table is parsed as Lua source (macro/form_code.py). Callbacks and other Lua expressions are shown as (Lua expression) and written back unchanged.
• GSAK-like canvas for layout = "absolute":
  • double-click to add a control
  • drag to move, drag the handles to resize
  • rubber-band and multi-select, with property changes applying to all selected controls
  • grid and snap-to-grid
  • align and same-size tools
  • copy, paste and duplicate
  • Ctrl/Shift+arrow keys to move or resize
• Automatic layout (layout = "auto"): an outline shows the fields top to bottom. Up/Down and Into/Out of group rearrange them.
• Tab order, button row (default OK/Cancel, none, or custom buttons), undo/redo, and Preview with the real FormDialog.
• Validation: before inserting, the form is checked with the same validation the runtime uses. If the macro would stop at an error, the designer warns you.
• GSAK import: paste a GSAK form (<Data> VarName=$form … <enddata>) from the clipboard, or import one from a .gsk/.txt macro (macro/gsak_form.py). The designer then lists what changed in the conversion so you can check it.

Changes

• src/opensak/gui/dialogs/form_designer.py: the designer dialog (new)
• src/opensak/macro/form_code.py: finds, parses and writes the Lua table without running it (new, Qt-free)
• src/opensak/macro/gsak_form.py: GSAK form → opensak.form{} converter (new, Qt-free)
• src/opensak/gui/dialogs/macro_dialog.py: new Tools menu and the insert/update logic
• src/opensak/macro/api_docs.py: the Forms section mentions the designer (CI regenerates api.md)
• New example macros/examples/corrected_coords_form.lua, with a form built in the designer
• Translations for all 11 languages

Tests

• tests/unit-tests/test_macro_forms.py: Lua table parse/write round trip, expressions kept as written, GSAK conversion
• tests/unit-tests/test_macro_form_dialog.py: designer canvas, selection, align tools, insert/update

How to try it

1. Open corrected_coords_form.lua, put the cursor inside the opensak.form{…} table, and open Tools → Form designer.
2. Move a control, click Update macro, then run the macro.
3. On an empty line, design a new form and click Insert into macro.
4. Paste a GSAK <Data> VarName=$form block through Paste form from clipboard and check the conversion notes.

Closes #982