macOS: in-place dist binary replacement SIGKILLs on next exec (code signing) -- document upgrade flow or add self-update

[Skippy-the-Magnificent-one]

Problem

Upgrading the compiled binary with cp new dist/mcp2cli (same inode, contents overwritten) invalidates the ad-hoc code signature on macOS. The next exec is killed by the kernel:

$ cp /tmp/build/dist/mcp2cli dist/mcp2cli && mcp2cli --version
# exit code 137 (SIGKILL)

Hit this on 2026-06-11 upgrading skippy-oc from 0.2.0 to 0.3.3.

Working upgrade flow (should be in README/CONTRIBUTING)

rm dist/mcp2cli                      # fresh inode is the fix
cp /path/to/new/mcp2cli dist/mcp2cli
launchctl kickstart -k gui/501/com.mcp2cli.local-ui   # restart local daemon

The already-running daemon keeps the old inode alive and is unaffected until restart, so this is safe to do live.

Nice-to-have

• mcp2cli self-update (or a scripts/install.sh) that does rm+cp+kickstart atomically.
• Version-skew warning: a 0.2.0 client talked to the 0.3.3 daemon with no complaint from either side -- 0.2.0 predates the source routing field entirely and just silently ignored it. mcp2cli daemon status could compare client vs daemon version and warn.