Extend std/cli.sx with a zero-heap argument parser that the caller drives
over a logical argv ([]string), separate from the F3.1 os_args accessor.
Grammar: <group> <command> [--flag VALUE | --bool]... [--json] [-- rest...]
- (group, command) dispatched against a caller-provided Command table;
no match -> error.UnknownCommand.
- value-taking vs boolean flags fixed by each command's FlagSpec list;
--json is a reserved global boolean surfaced as parsed.json.
- `--` or the first bare operand ends flag parsing; the remainder is
parsed.rest (operand views).
Heap discipline (heap-discipline.md): zero heap, zero copy. group/command/
flag values/rest are all VIEWS into args. Parsed is a by-value stack struct;
flag presence/values live in a fixed [16]FlagValue inline array indexed by
spec position (no per-flag allocation, no context.allocator). The flag-spec
list and command table are caller storage passed as views.
Failure surfacing (no silent skip): unknown command, unknown flag, a
value-flag missing its value, and an absent required flag each raise a
specific CliError variant; a caller-owned Diag records the offending token
(index + view) before each raise, since error tags carry no data.
examples/0717 drives the parser over explicit []string vectors: a valid
group/command/--flag/--bool/--json case (asserting parsed values + that
values are views into argv), subcommand dispatch, `--`/bare-operand
separators, and the five failure variants each asserted via destructure +
Diag. zig build && zig build test && run_examples.sh green (385 passed).
Add library/modules/std/cli.sx: a pure-sx command-line argument accessor
backed by the macOS C runtime (_NSGetArgv/_NSGetArgc), no compiler change.
os_argc() -> s64
os_args(buf: []string) -> []string
Zero heap, zero per-arg allocation: os_args fills a caller-provided buffer
(stack array) with string VIEWS over the process's own argv block, which
lives for the whole process. The returned slice header is a by-value stack
return; nothing touches context.allocator.
Documents the `sx run` reality: under `sx run <prog.sx> ...` the process
argv is the interpreter's argv (sx, run, prog.sx, ...), not a program's
logical args. This accessor reports the real process argv truthfully;
mapping to logical args is a later consumer concern (distribution P3.1).
Non-macOS platforms bail loudly (message + _exit) rather than returning a
silent empty.
examples/0716-modules-cli-argv.sx asserts only deterministic structural
invariants (argc >= 1, argv[0] non-empty, os_argc() == filled length).
