Arena round 6: revert railgun_m damage, correct playtest record

Arena re-run after the playtest-1 adjustments:

- spam-cruiser arena landed at par (default +9%) - the range buff alone
  priced out the small-gun-spam meta, so revert railgun_m damage 16 -> 14
  (range stays 80). The buff had regressed drone-swarm-vs-cruisers to
  +47%, largely via a hit-count breakpoint (60 HP drone: 5 hits at
  14 dmg, 4 at 16).
- battleship +30% / dreadnought +29% vs pure railgun_s fleets accepted
  as reach-doctrine texture (the l gun's 130 m standoff working as
  intended); repair kept at 4 HP/s (below par in-fight is the correct
  price for free between-wave sustain).

Also corrects the playtest-1 record: it was two FULL playthroughs won in
~40 min each with cruisers only (not two pushes) - a 2.5-3x run-length
gap. Pacing knobs deliberately deferred to playtest 2, since those runs
predate the repair nerf and the l-gun siege range.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DyCu8vwChKMbLJQ3xosYEN

bin/app/data/config/modules.toml

@@ -56,8 +56,11 @@ production_time_seconds = 3
 fill_color = "#FF8040"
 glyph = "Rm"
 
+# damage 14 keeps a 60 HP drone at 5 hits — 15+ crosses a breakpoint that
+# silently adds ~25% effective DPS vs drones (docs/balancing/history.md,
+# round 6).
 [module.weapon]
-damage = 16
+damage = 14
 attack_range_m = 80
 attack_rate_hz = 1.5