`activate` is bash syntax, so fish users had no way to take on the dev
environment. `activate.fish` does what `activate` does: snapshots the keys it
will change, applies the composed env, defines a `hermes` function that
refuses outside the worktree, adds the prompt prefix, and defines
`deactivate`. It shells out to the same bash library, so composition is not
reimplemented.
`pm.environments --format fish` emits the env as `set -gx` statements.
fish's read-only names (`PWD`, `SHLVL`, `_`, ...) are skipped because
`set -gx PWD` aborts the script, and values named `*PATH` stay lists.
`hermes_compose_env` takes the dialect (`sh` or `fish`) as its second argument.
`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.
