[ata-sesli]

What does this PR do?

Ports src/main.c, the last C module in the planned port order (internal/cbm is out of scope), to Zig. It follows the pattern used by the earlier ports.

The program behind main() moves to src/main.zig as cbm_main, declared in the new src/main.h. That covers:

• subcommand dispatch;
• the one-shot cli mode;
• the MCP server on stdio;
• the watcher re-index callback;
• the parent-death watchdogs;
• signal handling;
• the Windows UTF-8 argv rebuild.

checkExports in cbm_zig.zig checks cbm_main against its header.

Why main() itself stays in C

src/main.c shrinks from 857 lines to a short shim: int main(...) { return cbm_main(argc, argv, CBM_VERSION); }. Two constraints keep it in C:

• Duplicate main. The test runners link the same libcbm_zig.a and define their own main() in tests/test_main.c. The Zig library is one object, so a main exported from it would clash with theirs.
• Release version. The version is a C define: scripts/build.sh passes -DCBM_VERSION through CFLAGS_EXTRA. The Windows release links a Zig library that CI prebuilds in a separate job without that define. Reading the version in C keeps --version correct there.

Keeping the shim means no changes to build.zig, the Windows CI job or scripts/build.sh.

Other changes

• cbm_zig_c.h: includes main.h. On Windows it also includes shellapi.h (CommandLineToArgvW), tlhelp32.h (parent PID lookup) and signal.h.
• Makefile.cbm: lists src/main.zig and src/main.h as Zig library inputs.
• Comments: comments that pointed at main.c now point at main.zig.

Behavior

The port is meant to behave identically: same help text, exit codes, shutdown order and watchdog policy. One small difference: the cli path now frees its argument buffer when server creation fails, where the C version leaked it.

Verification

Run locally:

• libcbm_zig.a compiles for native macOS, x86_64-linux-gnu and x86_64-windows-gnu, the last two with Zova. cbm_main is exported and the library has no main symbol.
• zig fmt --check src build.zig passed.
• scripts/check-build-sources.sh passed.

Not run locally:

• No full binary link or runtime smoke test (--version, cli, MCP stdio). CI is the check for those.
• clang-format (not installed here).
• The test suite.

Checklist

• Commits are signed off (DCO)
• Tests pass (make -f Makefile.cbm test) — left to CI
• Lint passes (make -f Makefile.cbm lint-ci) — left to CI
• Test coverage — no new tests; the entry point has no test harness