Gateway: AP3X terminology in user-facing strings and docs

The signup page said '~5 ADA collateral' and two API error messages
told agents to 'deposit a little more ADA' - the coin is AP3X. Strings,
comments, and docs/gateway.md updated; code identifiers unchanged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

gateway/src/onchain/preflight.ts

@@ -3,9 +3,9 @@
  *
  * The buyer wallet funds the FULL escrow at PostEscrow: price + buyer_bond +
  * supplier_bond (postEscrow.ts:132). Accept/Reclaim are Plutus script-spends
- * that also need a pure-ADA collateral UTxO ≥ 5 ADA (assertCollateralCandidate).
+ * that also need a pure-AP3X collateral UTxO ≥ 5 AP3X (assertCollateralCandidate).
  * So required = price + buyer_bond + supplier_bond + collateral + fee reserve,
- * AND the wallet must currently hold a pure-ADA UTxO ≥ collateral. We check both
+ * AND the wallet must currently hold a pure-AP3X UTxO ≥ collateral. We check both
  * up front and return a clean 402 instead of failing mid-flight.
  */
 
@@ -18,7 +18,7 @@ export function totalLovelace(utxos: Utxo[]): bigint {
   return utxos.reduce((sum, u) => sum + u.lovelace, 0n);
 }
 
-/** True iff some UTxO is pure-ADA (no native assets) and ≥ collateral floor. */
+/** True iff some UTxO is pure-AP3X (no native assets) and ≥ collateral floor. */
 export function hasCollateral(utxos: Utxo[]): boolean {
   return utxos.some(
     (u) => u.lovelace >= COLLATERAL_MIN_LOVELACE && Object.keys(u.assets).length === 0,

gateway/src/openai/chatCompletions.ts

@@ -108,7 +108,7 @@ async function runOneShot(
     throw paymentRequired(
       pf.collateralOk
         ? "insufficient balance for this request"
-        : "wallet has no pure-ADA UTxO ≥ 5 ADA for collateral; deposit a little more ADA",
+        : "wallet has no pure-AP3X UTxO ≥ 5 AP3X for collateral; deposit a little more AP3X",
       {
         x_vector: {
           required_lovelace: pf.requiredLovelace.toString(),

gateway/src/openai/sessions.ts

@@ -93,7 +93,7 @@ export async function openSessionCore(
   const pf = await preflight(deps.chain, ctx.walletKey.address, primary);
   if (!pf.ok) {
     throw paymentRequired(
-      pf.collateralOk ? "insufficient balance to open a session" : "wallet has no ≥5 ADA pure-ADA collateral UTxO",
+      pf.collateralOk ? "insufficient balance to open a session" : "wallet has no ≥5 AP3X pure-AP3X collateral UTxO",
       {
         x_vector: {
           required_lovelace: pf.requiredLovelace.toString(),

gateway/src/ui/page.ts

@@ -33,7 +33,7 @@ export const INDEX_HTML = `<!doctype html>
 <div id="signupOut"></div>
 
 <h2>2. Fund your wallet</h2>
-<p class="muted">Send AP3X to your deposit address (you need price + bonds + ~5 ADA collateral + fees).</p>
+<p class="muted">Send AP3X to your deposit address (you need price + bonds + ~5 AP3X collateral + fees).</p>
 
 <h2>3. Account</h2>
 <div class="row">

gateway/src/walletHealth.ts

@@ -2,8 +2,8 @@
  * gateway/src/walletHealth.ts — keep each custodial wallet usable.
  *
  * After every settled request (and on a periodic tick) we re-shape the wallet to
- * {≥5 ADA collateral UTxO, working UTxO} via the shared consolidate builder, so
- * the NEXT request's Accept/Reclaim script-spend always finds a pure-ADA
+ * {≥5 AP3X collateral UTxO, working UTxO} via the shared consolidate builder, so
+ * the NEXT request's Accept/Reclaim script-spend always finds a pure-AP3X
  * collateral candidate. No-op when the wallet is already healthy.
  */