fix: apply mana drain to conversion disciplines (bug #379)

- Remove isConversionDiscipline guard in discipline-slice.ts:processTick
  that was skipping mana drain for all 24 conversion disciplines
- Update test to verify conversion disciplines DO drain mana
- Add regression tests for auto-pause and XP accrual on conversion disciplines
- Fix misleading comments in elemental-regen.ts and elemental-regen-advanced.ts

All 1196 tests pass.

docs/project-structure.txt

@@ -24,6 +24,7 @@ Mana-Loop/
 │   │   │   │   └── fabricator-spec.md
 │   │   │   ├── invoker/
 │   │   │   │   ├── systems/
+│   │   │   │   │   ├── invocation-system-spec.md
 │   │   │   │   │   └── pact-system-spec.md
 │   │   │   │   └── invoker-spec.md
 │   │   │   └── attunement-system-spec.md