#48 release install: project-generic artifact (any project), record-sha resolution

SOURCE: wr1te round 3 (verified): f0rge release install <ver> only works for f0rge's own self-update — the artifact name is hardcoded to f0rge, the cargo fallback assumes a cargo project whose binary is the artifact; project binaries always need manual install. And it required git tags that no command creates (covered by #47's record sha). FIX — make install PROJECT-GENERIC:

• artifact: if releases/build/<ver>/ has exactly one binary file, COPY it to $CARGO_HOME/bin/<that name> (any project, any language — wr1te's build drop becomes installable);
• cargo fallback ONLY when Cargo.toml exists AND no prebuilt artifact — resolve the bin name from [package]/[bin] and cargo install --locked from the resolved tree;
• resolution order: record sha (#47) > git tag > main = current checkout; --dry-run unchanged.
• AGENTS.md Install section reworded to the generic promise ("installs this project's release artifact"). DONE: a non-cargo project with a dropped artifact installs <ver> by copy; f0rge still self-installs; record-sha resolution works with zero tags; SEC argv-only holds.