Scale health and damage by ten so percentages have somewhere to land

A shot is 60, a fresh character has 1000, the Warden has 36000. Enemy health,
boss health and every emitter's damage were scaled with them, so every ratio
is unchanged and time to kill is exactly what it was -- tests/unit/test_content
now pins shots-to-kill per enemy and hits-to-kill a player so a careless edit
to either side shows up as a number a designer recognises.

The reason is rounding rather than balance. Damage is an integer, and at a base
of 6 the +5% every upgrade carries computed to 6.3 and rounded straight back to
6: a player took their first upgrade, was told it made them stronger, and
nothing happened. diag_upgrades used to print "damage matches the formula
(6 -> 6)"; it now prints (60 -> 63). The boss's per-phase armour multiplier had
the same problem, turning 1.15 into an effective 1.17.

The practice dummy stopped relying on a huge health pool at the same time. Its
old 100000 was already past the u16 the snapshot sends enemy health in, and
once a shot did 60 a patient player could have destroyed the hub's only
practice target for everyone until the next restart. EnemyDef.indestructible
says what was actually meant, and a test asserts nothing else uses it.

check.sh clean, 364 tests, SMOKE PASS, all four diagnostics green.

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

src/meta/progression.gd

@@ -10,8 +10,9 @@ extends RefCounted
 const MAX_LEVEL := 15
 const START_LEVEL := 1
 ## Hit points added per level gained. Level 1 is SimConfig.PLAYER_MAX_HP, so a
-## capped character has PLAYER_MAX_HP + 14 * this.
-const HP_PER_LEVEL := 10
+## capped character has PLAYER_MAX_HP + 14 * this. Scaled with everything else
+## -- see the note on SimConfig.PLAYER_MAX_HP.
+const HP_PER_LEVEL := 100
 
 ## Experience for the first level-up. The curve is tuned so one full clear of a
 ## depth-1 dungeon lands a little past this -- the first run should end with a