Fix muddy skull being unobtainable after dying with it

[HarleyGilpin]

Bug

Dying while carrying the muddy skull during The Restless Ghost permanently blocks the quest.

The rocks at the mining spot track whether the skull has been taken with the rocks_restless_ghost player var, and it was only reset from a playerDeath handler:

playerDeath {
    if (!ownsItem("muddy_skull")) {
        set("rocks_restless_ghost", "skull")
    }
}

Death.killed(player) runs synchronously in PlayerDeath before dropItems, so the skull is still in the inventory when the handler runs, ownsItem returns true and the var is never reset. The skull then drops to the gravestone, and once that expires searching the rocks only replies "You already have the ghost's skull." The quest dead-ends at found_skull because the coffin requires the skull to be carried.

Fix

Make ownership authoritative at search time rather than depending on death-hook ordering:

• Extracted the take logic into Player.takeSkull().
• Searching the emptied rocks now checks ownsItem("muddy_skull") (inventory, equipment, bank, beast of burden) and hands the skull back when the player no longer owns one.
• Removed the ineffective playerDeath handler. The destroyed handler stays so the rocks visually refill immediately when the skull is destroyed.

This covers every loss path - death, manually dropping it, and an expired gravestone - not just death.

Tests

Two tests added to RestlessGhostQuest:

• Search the rocks again after losing the skull on death - take the skull, die in the wilderness so it is dropped rather than kept, then re-search the rocks and get it back.
• Rocks stay empty while still carrying the skull - no duplicate skull while one is held.

The first test fails without the fix. All three tests in the class pass with it.