[alshdavid-machine]

Based on the reference in template-rust-cli's src/cmd/upgrade/main.rs.

procplot exec      # spawn a process and record its resource usage (previous behaviour)
procplot upgrade   # self-update to the latest release (alias: up, u; --check to only check)
procplot version   # print the current version

Changes

• procplot exec: the previous top-level behaviour moved under exec; args.rs and reporter.rs moved to src/cmd/exec/. All existing options (-r, -i, -m, -t, -o, --no-*) and PM_* env vars are unchanged; the command is still passed after -- (procplot exec -- node script.mjs).
• procplot upgrade: ported from the template — uses self_update (rustls) against GitHub releases of alshlabs/procplot, selects the asset matching OS/arch, and is skipped for prerelease versions. --check reports whether a newer release exists. Failures now propagate to the exit code instead of printing and returning 0.
• procplot version: prints CARGO_PKG_VERSION (the top level also has --version).
• Dependencies: self_update (github, reqwest, rustls, tar.gz, checksums) and semver.
• Docs: README usage/installation/upgrading updated; test/run.bash runs cargo run -- exec.

Notes for reviewers

• This is a breaking CLI change: procplot -- node ... no longer works; it must be procplot exec -- node ....
• Releases published before this change contain no recognisable binaries (and older tags are named 0.0.x), so procplot upgrade will report "already on the latest version" until a release built by the new workflow is the latest.

Verification (local)

• cargo clippy --all-targets --workspace -- -D warnings and cargo xfmt --check pass
• cargo build --release; procplot --help, procplot exec --help, procplot version behave as documented
• procplot exec -- node ... produces the expected CSV
• procplot upgrade --check queries GitHub correctly (reports 0.2.0 as latest, as no newer release exists)