[dwsuse]

Preparation for privilege separation (#3879) and the parser sandbox: no functional change. It restructures five places so that #4182 and #4183 can use the existing code paths instead of adding parallel ones. Rebased onto the new argconfig parser.

• Command lookup: handle_plugin() is split into plugin_lookup(), which parses the global options and finds what to do for a command line, and plugin_call_run(), which does it. The lookup runs nothing and prints only the usage errors of the global options. It no longer modifies the caller's argv in the "plugin-command" form.
• main() looks up first: main() calls plugin_lookup() once before it loads nvme-cli.conf and runs what it found afterwards. The config file skips the global options given on the command line, so the command line still wins; a count such as --verbose still adds up as if the file came first. nvme: drop root privileges through the privsep helper #4182 decides on the privileges between the lookup and the config file. (The old dry-run lookup with opterr = 0 is gone: the new parser has no quiet mode, and a second parse is not needed.)
• INI files: shr_ini_read_file() reads and checks a file like shr_ini_parse_file(), and shr_ini_parse_inplace() parses a buffer without copying it, so the strings point into the buffer.
• nvme-cli.conf: parsed in place; the strings of the global options point into the file buffer instead of one strdup() per value.
• --set-options: parsed into a list first, which is then applied to the global context; the parser no longer prints, the error is reported after applying the valid options in front of it, as before.

Testing:

• unit tests: plugin_lookup() picks the command handle_plugin() runs without running it or changing the arguments; the global options given on the command line win over the config file, counts add up, invalid values are still reported; shr_ini_read_file(), shr_ini_parse_inplace()
• full test suite (gcc, clang, --werror), every commit on its own
• FreeBSD and Windows (x86_64, aarch64) builds

[Copilot]

🟡 Changes recommended

Repeated verbosity keys change existing behavior, and global-option lookup tests pass without exercising successful parsing.

2 open issues

• Repeated verbose configuration values accumulate incorrectly · New
• Missing global option registration bypasses dispatch tests · New

What changed in this PR

Prepares nvme-cli for privilege separation and parser sandboxing by separating parsing from execution.

Changes:

• Splits command lookup from execution and performs lookup before loading configuration.
• Adds in-place INI parsing while preserving command-line option precedence.
• Separates --set-options parsing from application and adds unit tests.

File	Description
tests/​unit/​c/​test-plugin.c	Tests lookup against command dispatch.
tests/​unit/​c/​test-global-config.c	Tests command-line precedence and additive counts.
src/​plugin.h	Declares lookup and execution interfaces.
src/​plugin.c	Separates command selection from execution.
src/​nvme.c	Performs lookup before configuration loading.
src/​global-ctx.c	Separates option parsing from application.
src/​global-config.c	Parses retained buffers and preserves CLI overrides.
src/​argconfig.c	Resets option tracking on registration.
shared/​tests/​test-ini-util.c	Tests file reading and in-place parsing.
shared/​ini-util.h	Declares new INI interfaces.
shared/​ini-util.c	Separates INI reading from parsing.

_{Review effort: Balanced}