Bots never double jump or use the flat air dash

[WilsonNet]

Summary

EnemyBrain was written when jumping meant one ground jump. Two movement options
have since been added that it does not know exist:

• The double jump (AIR_JUMPS = 1, AIR_JUMP_VELOCITY = -620) — a bot jumps
  from the ground and never presses again in the air.
• The flat air dash — a bot dashes, but only to disengage on the ground. It
  never uses the fact that an airborne dash now holds its Y and crosses a gap in
  a straight line.

Why it matters

The canonical test is AI vs AI. diagnose.mjs --mode=online and
deathmatch-probe.mjs are the two runs that decide whether the game is healthy,
and neither can exercise a mechanic the bots do not use — so the double jump and
the air dash are currently only reachable by a human. That is the same blind spot
aim-probe.mjs exists for: a mechanic no bot touches is a mechanic nothing
measures.

It also makes bots read as worse than they are once humans are in the room. A
player who double jumps over a bot and dashes away is using two options the bot
cannot answer.

Evidence

movementSummary.wallJumps is routinely 0 across canonical runs, and no counter
exists for air jumps at all — which is itself part of the problem.

Suggested approach

1. Measure first. Add airJumps and airDashes to movementSummary in
   PhysicsDiagnostics, so "the AI never does this" is a number rather than an
   impression. Expect zero, then watch it become non-zero.
2. Teach EnemyBrain to spend the air jump when its target is above it and out
   of single-jump reach, and to air dash across a gap rather than walking around.
3. Keep the personality spread — a bot that always double jumps is as readable as
   one that never does. AIConfig.skillLevel is the existing knob.

Definition of done

• movementSummary.airJumps and airDashes non-zero across a handful of
  canonical runs, and still zero for a bot configured not to use them.
• arenaSummary.surfacesUsed does not regress — the point is more of the arena,
  not bots stuck on the ceiling.

Out of scope

• Changing the tuning of either mechanic. See specs/movement.md.