fix(loop-starter-kit): add btcAddress to BIP-322 curl examples

BIP-322 signature verification requires the btcAddress parameter in the
POST body. Without it, agents with native SegWit (bc1q) addresses receive:
"BIP-322 signature requires btcAddress parameter for verification"

Add btcAddress field to JSON bodies in:
- /api/register curl example (SKILL.md + .claude/skills/loop-start/SKILL.md)
- /api/heartbeat curl example (SKILL.md + .claude/skills/loop-start/SKILL.md)
- daemon/loop.md heartbeat phase description

Closes aibtcdev#7

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Author: dantrevino

.claude/skills/loop-start/SKILL.md

@@ -350,7 +350,7 @@ Register:
 ```bash
 RESPONSE=$(curl -s -w "\n%{http_code}" -X POST https://aibtc.com/api/register \
   -H "Content-Type: application/json" \
-  -d '{"bitcoinSignature":"<btc_sig>","stacksSignature":"<stx_sig>"}')
+  -d '{"btcAddress":"<btc_address>","bitcoinSignature":"<btc_sig>","stacksSignature":"<stx_sig>"}')
 HTTP_CODE=$(echo "$RESPONSE" | tail -1)
 BODY=$(echo "$RESPONSE" | head -1)
 if [ "$HTTP_CODE" != "200" ] && [ "$HTTP_CODE" != "201" ]; then
@@ -414,7 +414,7 @@ POST:
 ```bash
 HB_RESPONSE=$(curl -s -w "\n%{http_code}" -X POST https://aibtc.com/api/heartbeat \
   -H "Content-Type: application/json" \
-  -d '{"signature":"<base64_sig>","timestamp":"<timestamp>"}')
+  -d '{"btcAddress":"<btc_address>","signature":"<base64_sig>","timestamp":"<timestamp>"}')
 HB_CODE=$(echo "$HB_RESPONSE" | tail -1)
 HB_BODY=$(echo "$HB_RESPONSE" | head -1)
 if [ "$HB_CODE" != "200" ] && [ "$HB_CODE" != "201" ]; then

SKILL.md

@@ -350,7 +350,7 @@ Register:
 ```bash
 RESPONSE=$(curl -s -w "\n%{http_code}" -X POST https://aibtc.com/api/register \
   -H "Content-Type: application/json" \
-  -d '{"bitcoinSignature":"<btc_sig>","stacksSignature":"<stx_sig>"}')
+  -d '{"btcAddress":"<btc_address>","bitcoinSignature":"<btc_sig>","stacksSignature":"<stx_sig>"}')
 HTTP_CODE=$(echo "$RESPONSE" | tail -1)
 BODY=$(echo "$RESPONSE" | head -1)
 if [ "$HTTP_CODE" != "200" ] && [ "$HTTP_CODE" != "201" ]; then
@@ -414,7 +414,7 @@ POST:
 ```bash
 HB_RESPONSE=$(curl -s -w "\n%{http_code}" -X POST https://aibtc.com/api/heartbeat \
   -H "Content-Type: application/json" \
-  -d '{"signature":"<base64_sig>","timestamp":"<timestamp>"}')
+  -d '{"btcAddress":"<btc_address>","signature":"<base64_sig>","timestamp":"<timestamp>"}')
 HB_CODE=$(echo "$HB_RESPONSE" | tail -1)
 HB_BODY=$(echo "$HB_RESPONSE" | head -1)
 if [ "$HB_CODE" != "200" ] && [ "$HB_CODE" != "201" ]; then

daemon/loop.md

@@ -22,7 +22,7 @@ Unlock wallet if STATE.md says locked. Load MCP tools if not present.
 ## Phase 1: Heartbeat
 
 Sign `"AIBTC Check-In | {timestamp}"` (fresh UTC .000Z).
-POST to `https://aibtc.com/api/heartbeat` with `{signature, timestamp}`.
+POST to `https://aibtc.com/api/heartbeat` with `{btcAddress, signature, timestamp}`.
 Use curl, NOT execute_x402_endpoint.
 
 **Reads: nothing.** Addresses are in context from CLAUDE.md.