Adds two items from the "Code quality / tooling" section of
docs/future-work.md. Both make it easier to chase regressions
without touching codegen.
- `nescript build --no-opt` skips the IR optimizer pass so
optimizer-introduced miscompiles can be bisected against the
unoptimized output. Threaded through CompileOptions and gated
at the single optimizer call site in src/main.rs. Covered by a
new integration test that compiles the same program twice
(opt on / opt off) and asserts both outputs are valid iNES
ROMs with matching headers and reset vectors.
- A criterion-based `benches/compile.rs` harness that times the
full parse -> analyze -> lower -> optimize -> codegen -> link
pipeline on every examples/*.ne file. Sources are pre-read
into memory so file I/O stays off the hot loop, and each
example gets its own Criterion group for easy regression
spotting.
Committed ROM bytes under examples/*.nes are unchanged; the
emulator goldens under tests/emulator/goldens/ are untouched.
