Command-line options: help, version, trace, limits, input file

[paulhoadley]

The CLI accepts exactly one optional argument (the object file) and defaults to ./CODE. Useful additions, all implementable with plain argument parsing and no dependency:

• --help and --version (read from the jar manifest).
• --trace: print each instruction as it executes, with the program counter and the top of the stack. The single most useful thing for a student debugging their compiler's output.
• --code-size N and --data-size N to lift the 1,000 / 500 limits (needs the limits to be constructor parameters, Source-level tidy-up and Javadoc lint #36).
• --input FILE as an alternative to stdin redirection (helps on Windows and inside IDEs).
• Exit 2 for usage errors, distinct from the program's own failure status.

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Effort: M. Priority: P3. From the September 2026 project review (T25).