Promote Wild Gunman (U) from _wip to top-level project

Moves Wild Gunman (U) from _wip/ to Wild Gunman (U)/ with full ROM build:
- Adds header.s, chr.s, linker.cfg (HEADER+PRG+CHR segments)
- Updates Makefile to build and verify reconstructed.nes vs rom.nes
- Adds rom.nes copy + copilot/rom.nes symlink per repo convention
- Verified byte-identical build

Pass 1 complete: full code/data classification (~20% code / ~80% data)
Pass 2 partial: routine headers for all labels, semantic naming for key
routines (Reset, NmiHandler, MainStateDispatch, MainLoopBody, etc.),
zero-page aliases in locals.inc

Updates root OVERVIEW.md:
- Removes Wild Gunman from _wip skeleton table (23 -> 22 skeletons)
- Adds Wild Gunman as #13 in numbered inventory (BYTE-IDENTICAL, Pass 2)
- Updates summary count from 12 to 13 projects

Wild Gunman (U)/copilot/chr.s

@@ -0,0 +1,2 @@
+.segment "CHR"
+    .incbin "chr.bin"