Collaborative offboard: move the ark balance back on-chain

PrepareOffboard/FinishOffboard against captaind — per-input ownership
attestations, connector-based musig forfeits (with the deterministic
fanout tx when there is more than one input), and fee math that mirrors
the server bit-for-bit (weight fee rounds up, ppm-by-expiry rounds
down) since it rejects any other net amount. The receive pane gains a
'Move back on-chain' button that withdraws everything to the wallet's
own fresh address; the incoming tx is labeled 'Ark withdrawal' in
History and the ark side records the movement. Crash-safe: the txid
persists before FinishOffboard and resume asks GetVtxoStatus whether
the forfeits landed (the server broadcasts the tx itself).

Also fixes boarding to applySentTx after broadcasting the funding tx —
without it the spent coin lingered in the utxo set (a second board
double-spent it), and the post-board scan() could resurrect it by
racing the explorer's indexing.

Co-Authored-By: Claude Fable 5 <[email protected]>

1 files changed, 22 insertions, 1 deletions

diff --git a/src/ark/proto.js b/src/ark/proto.js
index 1cbc0ef..ae2342e 100644
--- a/src/ark/proto.js
+++ b/src/ark/proto.js
@@ -364,7 +364,11 @@ export function decodeVtxo(bytes) {
 export async function getArkInfo(ark) {
   const data = await grpcCall(ark, 'bark_server.ArkService/GetArkInfo', new Uint8Array(0));
   // Fee schedules a server never sends (or sends all-zero) mean "free".
-  const info = { boardFees: {}, refreshFees: { baseFeeSat: 0, ppmExpiryTable: [] } };
+  const info = {
+    boardFees: {},
+    refreshFees: { baseFeeSat: 0, ppmExpiryTable: [] },
+    offboardFees: { baseFeeSat: 0, fixedAdditionalVb: 0, ppmExpiryTable: [] },
+  };
   for (const { field, value } of pbFields(data)) {
     if (field === 1) info.network = td.decode(value);
     if (field === 2) info.serverPubkey = hex.encode(value);
@@ -374,6 +378,7 @@ export async function getArkInfo(ark) {
     if (field === 10) info.requiredBoardConfirmations = Number(value);
     if (field === 13) info.minBoardAmountSat = Number(value);
     if (field === 16) info.mailboxPubkey = hex.encode(value);
+    if (field === 20) info.maxOffboardInputs = Number(value);
     if (field === 18) { // FeeSchedule
       for (const f of pbFields(value)) {
         if (f.field === 1) { // board
@@ -385,6 +390,22 @@ export async function getArkInfo(ark) {
           }
           info.boardFees = b;
         }
+        if (f.field === 2) { // offboard
+          const ob = { baseFeeSat: 0, fixedAdditionalVb: 0, ppmExpiryTable: [] };
+          for (const g of pbFields(f.value)) {
+            if (g.field === 1) ob.baseFeeSat = Number(g.value);
+            if (g.field === 2) ob.fixedAdditionalVb = Number(g.value);
+            if (g.field === 3) {
+              const e = { thresholdBlocks: 0, ppm: 0 };
+              for (const h of pbFields(g.value)) {
+                if (h.field === 1) e.thresholdBlocks = Number(h.value);
+                if (h.field === 2) e.ppm = Number(h.value);
+              }
+              ob.ppmExpiryTable.push(e);
+            }
+          }
+          info.offboardFees = ob;
+        }
         if (f.field === 3) { // refresh
           const rf = { baseFeeSat: 0, ppmExpiryTable: [] };
           for (const g of pbFields(f.value)) {