Add zambo-receipts skill 🤖🤖🤖

docs/README.skills.md

@@ -475,3 +475,4 @@ See [CONTRIBUTING.md](../CONTRIBUTING.md#adding-skills) for guidelines on how to
 | [workshop-create](../skills/workshop-create/SKILL.md)<br />`gh skills install github/awesome-copilot workshop-create` | Create a new workshop or use an existing directory as one. Handles two paths: (A) use an existing local directory the operator points at, or (B) create a new private GitHub repo in the signed-in account. Never creates a repo inside another repo. | None |
 | [write-coding-standards-from-file](../skills/write-coding-standards-from-file/SKILL.md)<br />`gh skills install github/awesome-copilot write-coding-standards-from-file` | Write a coding standards document for a project using the coding styles from the file(s) and/or folder(s) passed as arguments in the prompt. | None |
 | [x-twitter-scraper](../skills/x-twitter-scraper/SKILL.md)<br />`gh skills install github/awesome-copilot x-twitter-scraper` | Build GitHub Copilot workflows with Xquik X API SDKs, REST endpoints, hosted Apify Actor runs, MCP tools, TweetClaw OpenClaw plugin installs, signed webhooks, tweet search, user lookup, follower exports, media actions, and agent automation. | None |
+| [zambo-receipts](../skills/zambo-receipts/SKILL.md)<br />`gh skills install github/awesome-copilot zambo-receipts` | Verify Zambo execution receipts. Every Zambo tool response includes a verifiable AER-1 receipt with an id, timestamp, and SHA-256 output digest. Use when you need to check that a Zambo tool call ran and that the saved result was not changed since it was saved. | None |

skills/zambo-receipts/SKILL.md

@@ -0,0 +1,67 @@
+---
+name: zambo-receipts
+description: Verify Zambo execution receipts. Every Zambo tool response includes a verifiable AER-1 receipt with an id, timestamp, and SHA-256 output digest. Use when you need to check that a Zambo tool call ran and that the saved result was not changed since it was saved.
+license: MIT
+compatibility: Requires network access to zambo.dev. Python 3 or curl.
+---
+
+# Verify Zambo receipts
+
+Every Zambo tool call returns a `_receipt` object alongside the result. It is the record of the call: which tool ran, when, and the SHA-256 digest of the exact saved output. Receipts follow AER-1, IETF draft-zambo-aer1-26.
+
+## What a receipt looks like
+
+```json
+"_receipt": {
+  "id": "f6ca2bd7-4e92-481e-be5c-ec20f3b69bac",
+  "tool": "live_price",
+  "timestamp": "2026-09-15T18:20:21.795Z",
+  "output_hash": "sha256:a6b360b683a91377fc16c452c4c064a7a68262d32adfb525c60d776d633e3ecf",
+  "status": "success"
+}
+```
+
+Each receipt also has a shareable human page at `https://zambo.dev/run/<id>`.
+
+## Handover receipts
+
+A Zambo handover (wrapping a session up so another AI can pick it up) produces receipts of its own: one for the wrap-up and one for the pickup (acceptance). Both verify exactly like any other receipt, with the same endpoint and the same digest check. A verified pickup receipt proves the receiving session accepted the recorded handover; together the pair proves the work crossed over with its record intact.
+
+## How to verify
+
+1. **Ask the verify endpoint.** Send a GET request to `https://zambo.dev/api/v2/receipt/{id}/verify`, replacing {id} with the receipt id. A genuine, unchanged record returns the outcome "verified". Or open https://zambo.dev/verify/ and enter the receipt id.
+2. **Fetch the stored record** from `GET https://zambo.dev/api/receipt/{id}` and read its `output_hash`.
+3. **Recompute the digest** of the exact output text you received and compare it to `output_hash`. A match means the saved result was not changed since it was saved.
+4. **Check the timestamp** is sane for when the call ran.
+
+```python
+import hashlib, json, urllib.request
+
+def verify_receipt(receipt_id, output_text):
+    url = f"https://zambo.dev/api/v2/receipt/{receipt_id}/verify"
+    with urllib.request.urlopen(url, timeout=15) as r:
+        verdict = json.load(r.read())
+    with urllib.request.urlopen(f"https://zambo.dev/api/receipt/{receipt_id}", timeout=15) as r:
+        stored = json.load(r.read())
+    claimed = stored["output_hash"].replace("sha256:", "")
+    actual = hashlib.sha256(output_text.encode()).hexdigest()
+    return {
+        "endpoint_outcome": verdict.get("verification_status") or verdict.get("outcome") or verdict.get("status"),
+        "hash_match": claimed == actual,
+        "timestamp": stored.get("timestamp"),
+        "status": stored.get("status"),
+    }
+```
+
+## What verification proves, and doesn't
+
+- **Proves:** the saved result was not changed since it was saved. The digest binds the receipt to the exact saved bytes; changing the output breaks the match.
+- **Does not prove:** the underlying data was right. A receipt shows the work was recorded as it happened; it does not certify, for example, that a price feed was accurate.
+- **Does not prove:** who authorized the call. Receipts record execution, not identity or permission.
+
+## Gotchas
+
+- **Hash the exact output text.** The digest covers the raw output string. Normalize nothing (no trimming, no re-encoding) before hashing.
+- **Receipts are public and shareable.** `https://zambo.dev/run/<id>` is designed to be linked in posts, reports, and PRs. Never put secrets in tool arguments; they may appear in shared receipts.
+- **Use the right words.** Never call a receipt "signed". The correct phrase is **verifiable receipt**.
+- **Missing receipt = incomplete response.** If a response has no `_receipt`, treat the result as unrecorded and say so.