Claude 3307f75da6 banks: implement multi-bank PRG layout and bank-switching runtime ... Prior to this commit the linker always shipped a single 16 KB PRG bank regardless of the declared mapper, so the README's MMC1/UxROM/ MMC3 support was aspirational. This commit gives the three banked mappers a real multi-bank ROM layout: * RomBuilder.set_prg_banks() writes any number of 16 KB banks back-to-back so the iNES header reflects the true PRG size. * Linker.link_banked() places switchable banks first, fixed bank last, so the fixed bank maps to $C000-$FFFF (the address window where vectors and the runtime live). * runtime::gen_mapper_init() emits reset-time mapper config: MMC1 serial-writes a control-register value that pins the last bank at $C000 with the correct mirroring, UxROM relies on the power-on default, MMC3 writes the $8000/$8001/$A000/$E000 registers to get a known PRG and mirroring state. * runtime::gen_bank_select() is a mapper-specific subroutine (callable with the target bank in A) that maps any physical bank to $8000-$BFFF. * runtime::gen_bank_trampoline() generates a cross-bank call stub in the fixed bank that saves the caller's bank, switches, JSRs the target, and restores the fixed bank. * The CLI and integration helper thread declared `bank X: prg` declarations through to the linker so MMC1/UxROM/MMC3 programs actually produce multi-bank ROMs. Coverage: * Runtime unit tests (18 new): mapper init patterns for every supported mapper, bank-select signatures, trampoline dispatch order, UxROM bus-conflict table contents. * RomBuilder tests (6 new): multi-bank layout, padding, byte-level fidelity, per-bank size validation, legacy single-bank fallback. * Linker tests (13 new): multi-bank ROM sizes across MMC1/ UxROM/MMC3, fixed-bank placement, switchable-bank payload fidelity, bank-select subroutine detection, NROM rejection of switchable banks. * Integration e2e tests (16 new): compile real .ne sources through the full pipeline and assert on iNES headers, mapper init signatures in the fixed bank, vector locations, and a regression check against `examples/mmc1_banked.ne`. Total: 474 tests pass under `cargo test` with `RUSTFLAGS="-D warnings"`. https://claude.ai/code/session_01UCressA5e8k1XsuoJYLav2		2026-04-13 01:50:51 +00:00
..
emulator	main: write the real mapper byte into the iNES header	2026-04-13 01:27:42 +00:00
integration
integration_test.rs	banks: implement multi-bank PRG layout and bank-switching runtime	2026-04-13 01:50:51 +00:00