[squad:plan] Echo Bloom — QA & Test Planning

**Owner:** Hockney (Test Engineer)

Workstream deliverables:
- Vertical Slice test plans covering plant interaction combinations
- Puzzle-break / softlock detection across chambers
- Demo regression coverage before Playable Demo ship

Part of the Echo Bloom game plan (#54786).

Read the Echo Bloom game plan in #54786 and this workstream’s deliverables first. Done means documented vertical-slice coverage for plant interaction combinations, checks for puzzle breaks and softlocks across chambers, and demo regression coverage before the Playable Demo ships.

Written by the indexing model from the issue text.