Put the rest of the selection settings on the Options card

Options → Selection already carried the pick box, the selection-area effect
and the grip visuals. Four settings behind it were finished, persisted and
reachable only by typing a system variable, and one more was a constant.

**Four that only needed a widget.** `SELECTIONEFFECT`, `SELECTIONPREVIEW`,
`PICKADD` and `PICKDRAG` are all wired end to end already. `SELECTIONEFFECT`
was the odd one: the card's own "Restore Defaults" button resets it, so it
could be turned off by a button and only turned back on from the command
line.

`SELECTIONPREVIEW` is a bitmask and gets one checkbox per bit, which is why
`set_preview_bit` exists rather than two inline expressions — the bits are
the thing this change is most able to get backwards.

The `PICKADD` checkbox is worded as AutoCAD words it, "use Shift to add to
selection", which is the *inverse* of the stored flag. That inversion is
commented at both ends; it reads as a bug otherwise.

**`GRIPOBJLIMIT`.** The limit past which a selection gets no grips arrived
with the selection work as a hardcoded 100, matching AutoCAD's default. It is
now a setting, a slider and a system variable, following `PICKBOX`'s path
exactly. AutoCAD's 0 means "no limit", which the old `>` comparison could not
express, so the read now guards on it — with a test, because zero is the one
value that would otherwise suppress every grip instead of allowing all of
them.

The slider covers 0..=1000, where every useful value lives; the sysvar takes
AutoCAD's full 0..=32767, and a larger value set from the command line parks
the handle at the end while the read-out keeps showing the real number.

**`SelectionPrefs`** replaces the `pick_box` parameter rather than adding
three more. `view_window` already took seventeen positional arguments, and
`pick_add` / `pick_drag_rect` are two adjacent `bool`s that would swap
silently at the call site.

**Two fixes found on the way.** `OPTIONS` and `OP` were registered for
autocomplete but never dispatched, so typing either answered "Unknown
command" and the dialog could only be opened from the start page. And the
`SELECTIONPREVIEW` doc comment had its bits the wrong way round — the code
reads `& 1` for the idle rollover and `& 2` for the in-command one, as
AutoCAD does — which would have put the two new checkboxes' labels backwards.

**Not done, deliberately.** `PICKFIRST` and `PICKAUTO` exist but are always
on, with no variable. `PICKSTYLE` is stored in the header and read by nobody
— group expansion decides from the group's own `selectable` flag — so an
"object grouping" checkbox would control nothing. Associative-hatch selection
does not exist as a selection behaviour. Each needs a behaviour change rather
than an exposure.

Of the ten new strings, en-US and el-GR are translated; the other nineteen
locales carry the English text. Composing them from existing keys, the way
el-GR composes the neighbouring labels, only works for one of the ten —
there is no existing key for "limit", "unlimited", "shift", "rectangle" or
"lasso", and "Grips: Objects" as the label of a numeric limit would be worse
than an untranslated string.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/app/commands/mod.rs

@@ -294,6 +294,10 @@ pub fn start_allowed(cmd: &str) -> bool {
             | "ALIASEDIT"
             | "CUILOAD"
             | "CUIIMPORT"
+            // The start page already offers Options as a button, so the
+            // command that opens the same dialog belongs here too.
+            | "OPTIONS"
+            | "OP"
     )
 }
 
@@ -548,6 +552,7 @@ inventory::submit!(crate::command::CommandRegistration {
         "GRIPCOLOR",
         "GRIPHOT",
         "GRIPHOVER",
+        "GRIPOBJLIMIT",
         // Reset selected entities' overrides to follow their layer.
         "SETBYLAYER",
         // Remove duplicate objects; set drawing base point; audit integrity;