Pushing

[nfagerlund]

OK, I think I've got this, uhhhhhh

• [x] Move system: Refactor to iterate over list of Entity IDs instead of whole borrowed query, so I can
• [x] Move system: ...sort entities by push priority (lowest priority goes first)
• [x] Move system: Include collided entity ID in published collision info, possibly reform to use events
• [x] Add PushPriority component to bundles -- you can push lower-priority things than you.
• [x] New Pushing component: target entity and activation dir (unit vec2 in a cardinal direction)
• [x] Push system (move planner): add your velocity to the guy you're pushing
• [x] Start pushing system: add Pushing if you collided with a pushable whose priority < yours.
• [x] Push system: remove Pushing if you stopped or turned around (activation_dir.x != velocity.x.signum(), or, y, depending.)

Limitations:

• you can only push one thing at a time
• no pushing stacks of things in a chain reaction (aw)
• can't push your equals, they're brick walls.

[nfagerlund]

• [x] What's up with sometimes blooping through a guy???

[nfagerlund]

Hell yeah, this now works AND feels super stable. The blooping through a guy (only when pushing in negative directions for some reason??) is resolved in e1c904b, by adding a small extra fudge factor to movement corrections for collisions. (Collider boxes were not reliably landing outside each other, apparently (??!) due to the innate imprecision of the calculations. Now they are.)