Get Pending Tree

Fetch a PENDING (staged, not-yet-on-chain) tree by its root hash.

A root is "pending" for a principal when it exists on one of their accessible vaults' protocol records but is not that vault's active on-chain root. Once the root is rotated on-chain it is no longer pending — this endpoint 404s for it and the base /trees/{root_hash} endpoint serves it instead.

Not cached (unlike the base endpoint): pending status is mutable — a root graduates on-chain (or is abandoned), which flips this endpoint's result — so the default no-store applies. The tree blob itself is content-addressed and immutable, but its accessibility here is not.