Add rust/crates/rusty-claude-cli/build.rs that:
- Captures git rev-parse --short HEAD at build time → GIT_SHA env
- Reads Cargo's TARGET env var → TARGET env
- Derives BUILD_DATE from SOURCE_DATE_EPOCH / BUILD_DATE env or
the current date via `date +%Y-%m-%d` fallback
- Registers rerun-if-changed on .git/HEAD and .git/refs so the SHA
stays fresh across commits
Update main.rs DEFAULT_DATE to pick up BUILD_DATE from option_env!()
instead of the hardcoded 2026-03-31 static string.
Before: `claw --version` always showed Git SHA: unknown, Target: unknown,
Build date: 2026-03-31 in local builds.
After: e.g. Git SHA: 7f53d82, Target: aarch64-apple-darwin, Build date: 2026-04-08
Generated by droid (Kimi K2.5 Turbo) via acpx (wrote build.rs),
cleaned up by Jobdori (added BUILD_DATE step, updated main.rs const).
Co-Authored-By: Droid <noreply@factory.ai>
