puzzles: resync with Simon's upstream e00cb46 from 25 Sep 2025.

Notably, this enables "Group".

This also includes some changes to the Rockbox frontend:

- Removes extraneous underline from Extensive Help text.

- Implements a workaround for an upstream breaking change that removes
  the BLITTER_FROMSAVED flag. We depend on this for mouse mode. This
  is apparently the only place this flag was ever used. Note that I've
  hardcoded an arbitrary negative value for BLITTER_FROMSAVED instead
  of -1, for the reason Ben Harris mentioned in his commit removing it
  from the upstream source tree.

- Adds an implicit clip() to the game region when drawing a
  puzzle. This fixes a bug in Untangle where dragging a point off
  screen leads to ugly lines outside the play area.

- Implements "Quick Help" for unfinished plugins (but not "Extensive
  Help").

- Documents the need to disable unfinished plugins in resync.sh (weak
  symbols on win32).

Change-Id: Ic318a5db4b15acb437a3f951fbc9b7919c6fa652

apps/plugins/puzzles/compress.c

@@ -158,7 +158,7 @@ int main()
     printf("};\n\n");
     printf("const unsigned short help_text_len = %d;\n", help_text_len);
     printf("const unsigned short help_text_words = %d;\n", word_idx);
-    printf("const bool help_valid = true;\n");
+    printf("const bool help_text_valid = true;\n");
 
     return 0;
 }