pczt: Add public getters for spend_auth_sig and shielded_sighash

pczt/CHANGELOG.md

@@ -10,6 +10,10 @@ workspace.
 
 ## [Unreleased]
 
+### Added
+- `pczt::orchard::Spend::spend_auth_sig` getter (via `getset`).
+- `pczt::roles::signer::Signer::shielded_sighash` getter.
+
 ## [0.4.1, 0.5.1] - 2026-02-26
 
 ### Fixed

pczt/src/orchard.rs

@@ -111,6 +111,7 @@ pub struct Spend {
     ///
     /// This is set by the Signer.
     #[serde_as(as = "Option<[_; 64]>")]
+    #[getset(get = "pub")]
     pub(crate) spend_auth_sig: Option<[u8; 64]>,
 
     /// The [raw encoding] of the Orchard payment address that received the note being spent.

pczt/src/roles/signer/mod.rs

@@ -95,6 +95,11 @@ impl Signer {
         })
     }
 
+    /// Returns the cached shielded (Orchard + Sapling) sighash.
+    pub fn shielded_sighash(&self) -> [u8; 32] {
+        self.shielded_sighash
+    }
+
     /// Signs the transparent spend at the given index with the given spending key.
     ///
     /// It is the caller's responsibility to perform any semantic validity checks on the