Don't save a number typed on the way to a wrong one

[PhilReinking]

Typing 2.5 into "Max characters" over 500 saved the 2 typed on the way, and 11 in "Height in lines" saved 1. The step's save waited for its debounce and went out after the next keys were refused. Now a number that turns wrong puts its option back into the waiting save, so the stored value stays.

Fixes BITS-351

• The workbench store keeps each answer as last sent while its changes wait. Only the long text settings use it; other settings save as before.
• The waiting save sends the stored value again (one request), so Saving… then Saved stays true.
• Other changes in the same waiting save, like a height changed just before, still go out.

Tested: Vitest types key by key through the real store and debounce; 3 of the 5 new tests fail without the fix. Lint and vue-tsc pass.

Browser, counting saves on my own server: main saves 2 and 1; this branch saves only 500 and 5, and 10 and 800 still save.

Not tested: Firefox and Safari (checked in Brave).

Known gap: an owner who rests over 1 second on 2 before typing .5 saves the 2, like any number they pause on.

🤖 Generated with Claude Code

[PhilReinking]

OK at 9694c62, CI green. Vitest 548, lint, vue-tsc clean; 3 new tests fail on main's code. Brave, key by key: 2.5 keeps 500, 11 keeps 5, both with the message; 10 and 800 save, ending Saved; -5, 0, -1 send nothing. Held: a slow save in flight, a failed save, a height change just before, a block switch, leaving the page. Scale settings save as before. A pause over 1 s on 2 still saves the 2.