Add onboarding-tester agent (docs-only fresh-adopter)

Global fleet agent that walks a product's published docs as a literal
newcomer, never reading its source, reports every doc gap, and emits a
publishable walkthrough only on a fully clean run. First instantiation:
keysat SDK integration. Register in fleet list, log ROADMAP item 9 and a
Current-state note, resolve the originating inbox item, and capture two
follow-ups (Path 2 payment demo, operator-onboarding agent).

ROADMAP.md

@@ -160,6 +160,30 @@ for repos that have a contract; (c) confirm against a real Claude Design run wha
 bundle actually contains and tune the Phase C distillation (the export internals are only
 medium-confidence from research).
 
+## 9. `onboarding-tester` — docs-only fresh-adopter agent ✅ BUILT (agent); harness pending
+
+Built and live: `guides/onboarding-tester.md` + `adapters/claude/agents/onboarding-tester.md`. A
+global adopter agent: given a **goal**, a **docs-corpus allowlist**, a **sandbox**, and
+**credentials/endpoint**, it walks a product's published docs as a literal newcomer — *never
+reading the product's source* (needing to is itself a finding) — and reports every doc gap
+(Blocker/Stumble/Nit + the one-line fix). On a **fully clean run** (zero blockers, zero stumbles)
+it emits a second, publishable "all it took was X, Y, Z" walkthrough for marketing. Generic by
+design; keysat is the first instantiation. The dual output (friction report always; marketing
+walkthrough only on a clean run) makes it both a docs-QA tool and a source of agent-readiness copy.
+
+**First instantiation — keysat SDK integration (harness lives in keysat, not here):** goal = gate
+`proof-of-work` behind a keysat license end-to-end under the least-privilege `merchant-onboard`
+scoped key (keysat shipped that role for this, commit `d5885d1`; covers catalog setup + manual
+license issuance, but **not** payment-provider connect, which stays master-only by design — a
+trust feature to surface, not a gap). Harness = two disposable containers (`keysat-server` fixture
+booted fresh + `developer-sandbox` holding `proof-of-work`), master-key mints the scoped key, docs
+corpus = keysat.xyz / docs.keysat.xyz / the four SDK package pages. **Pending:** build the harness +
+first live run in a keysat session.
+
+**Follow-ups (captured to `INBOX.md`):** (a) Path 2 — buyer-paid purchase demo (operator
+pre-connects a BTCPay/Zaprite sandbox once, agent drives the rest); (b) a separate
+operator-onboarding agent for the StartOS install journey.
+
 ## 7. Verify & correct the placement guide ✅ DONE (2026-06-15)
 
 Walked the "Infrastructure facts" section with the owner and corrected it against the real