Adv 2.0 D&D Phase 10 SUB3a-ii: Battle Master L10/L15

L10 Improved Combat Superiority — superiority dice grow d8 → d10. The
two scalar maneuvers (Precision Attack +4→+5; Rally heal +4→+5) bump in
their Apply hooks; Trip Attack has no scalar to scale.

L15 Relentless — 5e regenerates one die when initiative is rolled with
an empty pool. Proxied as +1 max pool size (4→5), which gives the same
"always at least one die per encounter" guarantee across the long-rest
cycle without introducing per-fight regen state.

subclassResourceMax now takes level; initSubclassResources upserts the
max (and bumps current by the delta) so existing characters grow on
level-up. Hooked into the dnd_xp level-up loop so Battle Masters
crossing L15 see the new die without waiting for a long rest. 4 new
tests; no regression in subclass/resource/level-up paths.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/plugin/dnd_subclass_cmd.go

@@ -123,7 +123,7 @@ func (p *AdventurePlugin) applySubclassChoice(
 	// Battle Master superiority dice). Idempotent. Failure is non-fatal —
 	// the player still gets the subclass; resources can be re-initialized
 	// next long rest.
-	_ = initSubclassResources(ctx.Sender, chosen)
+	_ = initSubclassResources(ctx.Sender, chosen, c.Level)
 	// Phase 10 SUB2-AT — Arcane Trickster bootstraps a Mage-list spellbook
 	// + third-caster slot pool on selection. Idempotent and non-fatal: the
 	// next `!cast`/`!spells` call also runs ensureSpellsForCharacter.