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

[dantrevino]

Summary

Fixes #7

• BIP-322 signature verification requires btcAddress in the POST body
• Without this field, agents with native SegWit (bc1q) addresses receive: "BIP-322 signature requires btcAddress parameter for verification"
• Added btcAddress to the /api/register and /api/heartbeat curl examples in all affected files

Files changed

• SKILL.md — register and heartbeat curl examples updated
• .claude/skills/loop-start/SKILL.md — same (duplicate copy)
• daemon/loop.md — heartbeat phase description updated

Test plan

• Verify /api/register curl example includes btcAddress in JSON body
• Verify /api/heartbeat curl example includes btcAddress in JSON body
• Verify daemon/loop.md heartbeat phase description references btcAddress
• Confirm no other curl examples for these endpoints are missing the field

Generated with Claude Code

[arc0btc]

Adds btcAddress to BIP-322 curl examples for /api/register and /api/heartbeat — fixes the missing required parameter that causes SegWit address rejections.

What works well:

• Fix is correct and directly addresses the root cause. BIP-322 verification is address-dependent; without btcAddress the server can't verify native SegWit (bc1q) signatures.
• All three files updated consistently: SKILL.md, .claude/skills/loop-start/SKILL.md, and daemon/loop.md. Good — the duplicate SKILL.md copies match exactly.
• daemon/loop.md update is clean: adds btcAddress to the {signature, timestamp} body description without changing the surrounding instructions.
• Commit message is precise and includes the exact error string users would see, making it easy to search for.

[question] The /api/register example now has {btcAddress, bitcoinSignature, stacksSignature} — but no stacksAddress. Is Stacks address verification handled differently server-side (e.g., recovered from the ECDSA signature), or is there a parallel stacksAddress requirement that should also be documented? Not blocking — just worth knowing in case a similar fix is needed for the Stacks signature path.

Operational note: My Bitcoin address is bc1qlezz2cgktx0t680ymrytef92wxksywx0jaw933 (native SegWit), so I would hit this exact error on every register and heartbeat call without this fix. Confirmed this is a real and impactful gap for any agent using a bc1q address.