Phase 2 follow-up to #2510 — wires acquisition for the gargoyle Throwing content that Phase 1 deliberately left out.
## Changes
- **SA loot flavor (`IsStygian`)** — completes the dead loot path from the original PR: adds `SAWeaponTypes`/`SARangedWeaponTypes` pools + `isStygian` branches to `Loot.RandomWeapon`/`RandomRangedWeapon`, **and** the missing piece — computes `IsStygian` (`map == Map.TerMur`) in `LootPackEntry.Construct` and threads it through `LootPackItem.Construct`. Ter Mur creatures now roll SA gear + the three throwing weapons (Boomerang/Cyclone/SoulGlaive) from their normal `BaseWeapon`/`BaseRanged` loot entries. Conservative `TerMur`-only (not ServUO's extra `|| RandomBool()`).
- **Valkyrie's Glaive** — re-added as a self-contained Ter Mur stealable artifact at `(843, 665, 27)`, matching ServUO/OSI, with the previously-missing `ArtifactRarity => 5`.
## Deferred (documented)
The 5 host-dependent artifacts (Raptor Claw, Stone Slith Claw, Storm Caller, Banshee's Call, Wind of Corruption) are intentionally NOT included — their OSI drop sources (Raptor, StoneSlith, and the renowned/boss creatures + a `BaseRenowned` artifact-list system) don't exist in ModernUO yet, so re-adding the items now would leave them `[add`-only. They'll follow a dedicated SA-creatures effort.
## Notes
- No new tests: both changes are property/plumbing with RNG-driven output — no deterministic complex logic to assert (consistent with the repo's test-scope conventions).
- Verified: server + test project compile; throwing suite 14/14.
### Summary
* Adds logging if Amount goes to zero. It should never go to zero!
* Deletes an item if it mutates with zero amount.
* Eliminates possible allocation from `params` for `Type[][]` loot pack construction.
* Renames `Loot.ChestOfHeirloomsContains` to `Loot.RandomChestOfHeirloomsContent`.
