feat(modify): TXTEXP turns text into its character outlines

TXTEXP replaces each selected TEXT and MTEXT with one polyline per
glyph contour, on the text's layer and with its properties: a
lightweight polyline for flat text, a 3D polyline for tilted text.
The outlines come from the same glyph tessellation the text renders
with, so stroke fonts give their strokes and outline fonts their
closed contours.

Refs D#1665

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/app/control/mod.rs

@@ -277,6 +277,7 @@ fn command_category(name: &str) -> &'static str {
         "BREAK",
         "JOIN",
         "EXPLODE",
+        "TXTEXP",
         "STRETCH",
         "ARRAY",
         "PEDIT",
@@ -349,6 +350,7 @@ fn command_selection_policy(name: &str) -> &'static str {
         "CUTCLIP",
         "ERASE",
         "EXPLODE",
+        "TXTEXP",
         "GROUP",
         "LAYFRZ",
         "LAYLCK",