Make the arenas' cover actually stop bullets

The player's muzzle was fixed last commit; every enemy and boss emitter
has one too, and theirs reach further. A ring sits 46px out, an arc
sweep's outer arms sit past 100px, and a wall-gap curtain spans the whole
arena -- most of a curtain is nowhere near the thing that fired it. The
pool samples geometry once per tick and never sees the jump, so all of
those were spawning bullets on the far side of whatever stood between.

That matters here more than it sounds, because both boss arenas are
authored out of cover. The hall has pillars; the vault has barricades,
and its own comment says they are there so that knowing where the Cantor
is does not hand you a firing lane to it. A barricade blocks bullets and
deliberately does NOT block sight -- so it is exactly the cover this bug
cancelled. Measured before fixing: the Warden's curtain put 13 shots
through a one-tile wall and its arc sweep 13 more; the Cantor's curtain,
16.

Two checks, not one. The path test skips its own starting tile so a
shooter in a doorway still resolves, and that skip let a telegraphed
burst whose centre and ring sit inside one wall tile through -- born in
the wall, announced to every client, dead on the next tick. The
destination is now asked separately, so a bullet never exists inside
geometry.

A telegraphed strike passes its own marker as the source rather than the
boss: that burst is born where the player was warned, and a pillar
between the boss and the spot has nothing to say about it. A strike
marked on cover is now simply a dud, which is cover working; pinned by a
test so it stays a known shape.

First attempt at this used a turret behind a barricade and proved
nothing -- a turret's 24px offset cannot clear its own 16px radius plus a
32px tile, so the test could not have failed. Replaced with the two
emitters that can reach, plus both real arenas.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/sim/patterns/telegraphed_strike_emitter.gd

@@ -59,7 +59,10 @@ func _burst(ctx: EmitContext, at: Vector2) -> void:
 		return
 	for i in burst_count:
 		var a := TAU * (float(i) / float(burst_count))
-		emit_shot(ctx, a, at + Vector2.RIGHT.rotated(a) * (blast_radius * 0.25))
+		# From the marker, not from the boss: this burst is born where the
+		# player was warned it would be, and a pillar between the boss and the
+		# spot has nothing to say about it.
+		emit_shot_from(ctx, a, at + Vector2.RIGHT.rotated(a) * (blast_radius * 0.25), at)
 
 
 ## Where volley [param volley]'s strike [param index] lands, inside