feat: implement ? / ?? print command (#2)

[DDecoene]

Closes #2.

Implements the most-typed dBASE III command: ? evaluates an expression (or comma-separated list) and prints the result.

? 2 + 2
         4
? UPPER("hello")
HELLO
? "a", "b"
a b

Implementation (wiring, per the issue)

• Lexer — tokenize ? and ?? as OP tokens.
• Parser — new PRINT AST node + parsePrint(); dispatched before the keyword switch since ? is an operator token. Parses zero-or-more comma-separated expressions.
• Executor — doPrint() + fmtPrint(): strings unquoted, booleans .T./.F., numbers right-justified in a 10-wide field (matching STR()'s default). Bare ? prints a blank line.

Note on ??

?? is recognized, but its dBASE "continue on the same line, no leading newline" semantics aren't expressible in the line-based web terminal (each output line is its own DOM row), so it currently shares ?'s formatting. Documented in code + CHANGELOG.

Tests

• tests/Print.test.ts — 7 cases (arithmetic + right-justify, unquoted strings, comma list, blank line, booleans, ??, not-unknown). All green.
• Full suite: 209 passing, tsc --noEmit clean.

Targets release/v1.0.0 per GitFlow (milestone v1.0.0).