fix(setup): real per-step resumption + exception/env/mkdir discipline + tighter tests
- Per-step resumption: skip steps whose prior status is `ok` and whose recorded paths exist; service step probes health and restarts when wedged before reinstalling.
- Exception discipline: wrap each step in try/except; record `failed` row, flush manifest, return exit 1 for ordinary exceptions. KeyboardInterrupt/SystemExit propagate.
- `SOLSTONE_JOURNAL` is honored in `resolve_journal_path`, mirroring `get_journal_info` resolver order.
- `step_journal` mkdirs the journal directory before writing config; `--journal <regular-file>` is rejected at `resolve_context` with a dead-end.
- Tests: replace substring `command_contains` with positional `assert_command`; add resumption / wedged-service / env-precedence / dead-end / exception / port-propagation cases.