Live, watchable 2-agent ETH-escrow demo (mock chain) — stacked on #131

[Pattermesh]

SIMULATED / MOCK CHAIN — not a live network. No real ETH, no real RPC, no network, no funds. Everything runs against an in-memory MockChain implementing the AgentEscrow surface (lock → confirm → release / refund). Synthetic agents/keys only. Nothing here is a live or production deployment.

Stacked on #131. Base is pattermesh/switchboard-agentic-demo-pwa (the head of #131), not main. Review/merge #131 first; retarget this PR to main after #131 merges.

Makes the existing examples/agentic_demo agent-to-agent flow watchable in a browser — the headline asset for showing off switchboard's agentic-payments rail.

Run it (the one command a human types)

cd <repo>
PYTHONPATH=. python examples/agentic_demo/server.py
# then open http://127.0.0.1:8402/   (or add --open)

GET / serves a single self-contained page; press Run demo.

What the viewer sees

Two agents transact over a mock-Ethereum AgentEscrow, animated step by step:

1. Agent A hires Agent B for an inference job.
2. B → 402 Payment Required with an x402 escrow PaymentOffer (5 USDC).
3. A's real X402Middleware validates the offer against a cap, recipient allow-list, and gas budget.
4. Escrow LOCK — A locks 5 USDC in AgentEscrow (state Locked); A's balance 100 → 95 USDC.
5. B delivers the work (HTTP 200) against the payment proof.
6. Escrow RELEASE — A confirms; escrow Locked → Released; B credited 5 USDC.
7. SafeSwap — B routes the received USDC through the SafeSwap orchestrator into the target asset (ETH/LUX), with a real best-execution route + receipt.

Every number on the page is the real orchestration's output — real escrow state, real X402Middleware.get_spend_summary(), real SafeSwap receipt — replayed step by step, not recomputed/faked in JavaScript.

How it's built (nothing core is rewritten)

scenario.py / onchain.py / safeswap.py are byte-for-byte unchanged. The live layer is purely additive:

File	Role
observable.py	wraps run_scenario into an ordered, deterministic, render-ready timeline (logical clock + seeded ids ⇒ same seed yields byte-identical runs)
server.py	stdlib http.server transport: GET /, POST /api/demo/run, GET /api/demo/state, POST /api/demo/step, GET /healthz
web/	canonical page sources (index.html, demo.css, view.js, demo.js); build.mjs inlines them into the self-contained demo.html the server serves
test_live.py, web/demo.test.mjs	pin timeline order, determinism, the HTTP envelope, and the demo.html build-sync
DEMO.md	the fixed design contract (event model, step ids, HTTP API)

JSON API (see DEMO.md):

POST /api/demo/run    → run the scenario, return the ordered timeline + summary envelope
GET  /api/demo/state  → replay the last run (or a fresh seeded one)
POST /api/demo/step   → optional server-driven stepwise mode
GET  /healthz         → {"ok": true}

Verification

• PYTHONPATH=. python3 -m pytest examples/agentic_demo/ -q → 29 passed; existing tests/test_agentic_demo.py → 11 passed (unchanged scenario still green). Broader suite: 245 passed, 62 skipped, 0 failed.
• node --check on every web/*.js → clean; node --test examples/agentic_demo/web/demo.test.mjs → 20 passed.
• Live smoke: started the server, GET / → 200 HTML (sandbox banner + canvas present); POST /api/demo/run → ordered timeline setup → 402 → validate → pay → deliver → settle → swap.quote → swap.execute, escrow Locked → Released, payee B credited 5.00 USDC, A debited to 95.00 USDC, settled: true; GET /api/demo/state echoes the last run.

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Live demo by Pattermesh (Patty / P. Sundaram). The escrow / x402 / SafeSwap orchestration shown here is kcolbchain/switchboard's — the collective's agentic-payments rail (Abhishek Krishna / @abhicris leads). This PR only makes it watchable.

🤖 Generated with Claude Code

[abhicris]

🤖 Audit skipped — diff is 206KB (limit 64KB). Labelling for human review.