feat(cli): orch8 dev — ephemeral engine with hot reload and virtual time

[ovasylenko]

Summary

Item #9 from docs/FEATURE_OPPORTUNITIES.md, the last one: orch8 dev [path] — the local dev loop. Starts an ephemeral in-process engine (in-memory SQLite via the orch8 facade crate — dogfooding the public API), loads sequence.json (or --sequence <file>), creates an instance, and drives fast ticks with live step-by-step output.

• --skip-timers: injects a ManualClock (facade builder gained .clock(...)); when a tick is idle but the instance has a future next_fire_at, the clock advances to it. A workflow with a 3-day delay completes in milliseconds — verified by running the binary:

  09:31:54.003 ⏩ clock advanced to 2026-06-13 09:31:55 UTC
  09:31:54.004 ✓ wait  noop
  ── instance completed ── 3 step(s), 0.0s elapsed
  

• Hot reload: zero-dep mtime poll; valid changes upsert a NEW immutable version + fresh instance ("reloaded vN" banner), invalid JSON prints the error and keeps the old version running.
• --mock handler='{json}' (repeatable) registers stub handlers; failing steps print a hint naming the unregistered handler. --dry-run flows to the instance flag (facade CreateInstanceOptions extended). --once exits 0/1 on completed/failed for CI smoke use. Ctrl-C shuts down gracefully with a session summary.

Tests

24 new tests in the dev module (mock parsing, sequence loading/invalid-JSON, mtime-poll reload detection, next_advance_target pure-function logic, skip-timers e2e through the facade: delayed sequence completes near-instantly). cargo test -p orch8-cli -p orch8: 61 passed. fmt/clippy(pedantic)/doc/check gates clean. Binary smoke-tested manually.

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