feat(server::grpc): wire Shamir committee bootstrap and unseal proto messages

Adds DeclareCommittee and ContributePassphrase variants to bootstrap.proto,
ContributePassphrase to unseal.proto, and AwaitingContributions result codes
to both. Implements corresponding inbound converters and outbound reply
mappings. VaultGate handlers delegate to VaultCoordinator.

server/crates/arbiter-server/src/peers/operator/vault_gate/mod.rs

@@ -3,6 +3,7 @@ use crate::{
     actors::{
         GlobalActors,
         vault::{self, Bootstrap, GetState, TryUnseal, VaultState, events},
+        vault_coordinator::{ContributeBootstrap, ContributeUnseal, StartBootstrap},
     },
     crypto::integrity::{self},
     db::DatabasePool,
@@ -17,6 +18,9 @@ use tokio::sync::oneshot;
 use tracing::{error, info};
 use x25519_dalek::{EphemeralSecret, PublicKey, SharedSecret};
 
+pub use VaultGateMessage as Inbound;
+pub use VaultGateMessageReply as Outbound;
+
 pub mod state;
 
 #[derive(Debug, thiserror::Error)]
@@ -118,8 +122,7 @@ impl VaultGate {
         }
     }
 }
-
-#[messages(messages = Inbound, replies = Outbound)]
+#[messages(enum)]
 impl VaultGate {
     #[message]
     pub fn handle_handshake(
@@ -234,6 +237,52 @@ impl VaultGate {
 
         Ok(answer)
     }
+
+    #[message]
+    pub async fn handle_declare_committee(&mut self, count: usize) -> Result<(), Error> {
+        self.actors
+            .vault_coordinator
+            .ask(StartBootstrap {
+                operator_id: self.auth_creds.id,
+                declared_count: count,
+            })
+            .await
+            .map_err(|_| Error::internal("VaultCoordinator unavailable"))
+    }
+
+    #[message]
+    pub async fn handle_contribute_bootstrap_passphrase(
+        &mut self,
+        passphrase: Vec<u8>,
+    ) -> Result<bool, Error> {
+        use arbiter_crypto::safecell::SafeCell;
+        let passphrase_cell = SafeCell::new(passphrase);
+        self.actors
+            .vault_coordinator
+            .ask(ContributeBootstrap {
+                operator_id: self.auth_creds.id,
+                passphrase: passphrase_cell,
+            })
+            .await
+            .map_err(|_| Error::internal("VaultCoordinator unavailable"))
+    }
+
+    #[message]
+    pub async fn handle_contribute_unseal_passphrase(
+        &mut self,
+        passphrase: Vec<u8>,
+    ) -> Result<bool, Error> {
+        use arbiter_crypto::safecell::SafeCell;
+        let passphrase_cell = SafeCell::new(passphrase);
+        self.actors
+            .vault_coordinator
+            .ask(ContributeUnseal {
+                operator_id: self.auth_creds.id,
+                passphrase: passphrase_cell,
+            })
+            .await
+            .map_err(|_| Error::internal("VaultCoordinator unavailable"))
+    }
 }
 
 impl Message<events::Bootstrapped> for VaultGate {