`activate` doubled as the thing scripts sourced non-interactively, so it
carried `--` argument guards and every caller had to tolerate its prompt and
`hermes` function. Composition (setup sync, bootstrap Python, pm env) now
lives in scripts/_activation.sh, and there are two consumers:
- `activate`: interactive, reversible (`deactivate`).
- new `scripts/run-in-hermes-env CMD...`: applies the env to one process and
execs into it. Replaces `scripts/_hermes-python`; every Python script's
shebang and `scripts/run_tests.sh` (which re-executes itself under it,
however it was launched) use it.
`pm.environments --format sh` emits the env as shell exports, so the inline
JSON-to-export Python is gone from `activate`. An install that did not build
the test environment now reads as stale for every consumer.
Tests are split along the same seams: activation support fixtures, bash/ps1
activation, env-script quoting, and the runner's staleness.
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