Promote Xevious (U) and Zanac (U) from _wip/ to NROM/

- Xevious (U): Promoted from _wip/NROM/Xevious (U)/ to NROM/Xevious (U)/
  - Pass 3 complete: 34.5% code coverage, 143 semantic entry points,
    4 named data tables, ~20 semantic ZP aliases
  - NROM mapper 0, 32 KB PRG, 8 KB CHR, horizontal mirroring

- Zanac (U): Promoted from _wip/UNROM/Zanac (U)/ to NROM/Zanac (U)/
  - Pass 3 complete: 34.5% code coverage (bank 7 only), 133 semantic
    entry points, 26 named data tables, 14 semantic ZP aliases
  - UNROM mapper 2, 128 KB PRG (8 banks), no CHR
  - Bank 7 fixed at CPU -; banks 0-6 switchable at 000-
  - Bank 7 assembled separately as prg.07.s with .org

Both projects build byte-identical. Updated root README.md inventory,
per-project details, and WIP.md accordingly.

Move Zanac (U) to UNROM/ mapper directory

Zanac (U) is a UNROM (mapper 2) game, not NROM (mapper 0). Move it to
the correct mapper directory and update README.md and WIP.md references
accordingly. Update project counts in WIP.md (857->856 total, UNROM
98->97 projects).

Promote Mermaids of Atlantis (U) from _wip/ to MAPPER8/

Additional cleanup of Mermaids of Atlantis

MAPPER8/Mermaids of Atlantis (U)/README.md

@@ -0,0 +1,61 @@
+# Mermaids of Atlantis (U)
+
+## Status
+
+**Pass 1 complete.** The code/data split has been produced by `nesdis.py` and
+the project builds byte-identical to the original ROM. `prg.s` now contains
+traced code with audit comments and `.byte` data blocks for unreached bytes.
+
+`make` assembles `header.s`, `prg.s`, `chr.s`, links them with `ld65` and compares the
+result against `rom.nes`:
+
+```
+Byte-identical ROM verified.
+```
+
+## ROM
+
+| Property | Value |
+|----------|-------|
+| Format | iNES |
+| Mapper | 8 |
+| Board | MAPPER8 |
+| Mirroring | Vertical |
+| Four-screen VRAM | no |
+| Battery | no |
+| PRG | 64 KB (4 x 16 KB), at file offset $0010 |
+| CHR | 64 KB (8 x 8 KB) |
+| Trainer | none |
+| Footer | none |
+| NMI vector | $8189 |
+| RESET vector | $FF00 |
+| IRQ vector | $8036 |
+| ROM file | `Mermaids of Atlantis (U).nes` |
+| SHA-256 | `53f5d22650063aba89b91762f133d1b6b2680c505b193d88a472580d09701122` |
+
+### Header notes
+
+- none
+
+## Open work
+
+- **Pass 2** - replace the address-derived `Label_XXXX` names and the raw
+  `$XXXX` call operands.
+- **Pass 3** - semantic zero-page aliases (applied only at the sites where
+  their role is proven) and named data tables.
+- **Promotion** to `NROM/<name>/` once Pass 3 is done, as `git mv`.
+
+## Files
+
+| File | Purpose |
+|------|---------|
+| `prg.s` | Pass 1 PRG disassembly (traced code + data blocks) |
+| `header.s` | iNES header include |
+| `chr.s` | CHR include |
+| `prg.bin` | 65536 bytes (64 KB) PRG image |
+| `chr.bin` | 65536 bytes (64 KB) CHR image |
+| `rom.nes` | byte-identical copy of the original ROM |
+| `linker.cfg` | HEADER / PRG / CHR memory areas |
+| `symbols.inc` | NES hardware register names |
+| `locals.inc` | zero-page aliases (5 ZpXX aliases at Pass 1) |
+| `Makefile` | build and byte-identity check |