Revive the swap MCP tools: PR #69 merged to the wrong base and never reached main

[hellno]

Part of #23. References #26 (stays closed) and PR #69.

Corrected 2026-07-10 (codebase re-verified): the "cherry-pick ecfe2ac / ~1,770 LOC absent" framing was wrong. The daemon + core + wire + GUI swap path already landed on main via #24/#25. What is actually missing is only the MCP-sidecar layer + the demo stub + the e2e harness. Re-scoped below.

What actually happened

PR #69 — "Swap v1 agent + demo: 3 MCP tools, fork-demo stub, swap-e2e" — merged onto branch hellno/test-merged-prs-gui, not main, so its work never reached trunk. But most of what it delivered has since arrived on main independently, so this is NOT a clean cherry-pick.

Already on main (do NOT rebuild — verified 2026-07-10)

• Full CoW orderbook client cow_client.rs with the cow-client feature default-on.
• SwapOrder + ProposeOrder / SignOrder / CancelOrder wire, dispatched by the daemon (daemon.rs:363/369/375, sign_order at :940) including the shaped GPv2 relayer-approve (daemon.rs:541-563).
• evaluate_order policy admission (policy.rs:807; always NeedsApproval, receiver==wallet, token allowlist).
• The Swap GUI (swap.rs / swap_view.rs) and app swap_quote plumbing.
• Swap parity tests (signerd/tests/swap_parity.rs).

So the trust-critical, test-covered swap engine is present.

What is actually missing (the real scope of this issue)

Verified absent from main:

• 3 MCP tool wrappers in deckard-mcp/src/server.rs (deckard_swap_quote, deckard_swap, deckard_submit_order) — the sidecar today has 8 tools and none are swap tools.
• The sidecar.rs wire-call methods for orders (today only a "swap" log string exists there).
• DECKARD_DEMO_SWAP_STUB in env.rs (deterministic fixture quote + simulated fill via anvil setStorageAt, every stubbed response marked simulated:true) — not on main.
• swap_e2e.rs (~339 LOC) and the env-gated just swap-e2e live-Sepolia harness — not on main.
• Doc reconciliation: tool count everywhere goes 8 → 11 (server.rs self-description, README, docs/build/30-mcp-shape.md, 31-agent-quickstart.md, STATUS). deckard_execute stays tx-only.

Because server.rs went 5 → 8 tools and env.rs/sidecar.rs were reorganized since June 16, ecfe2ac cherry-picks with conflicts in server.rs, sidecar.rs, env.rs, tests/common/mod.rs — treat this as a re-implementation onto today's main, not a cherry-pick. No new deps (cow-client already default-on).

Sizing & priority

More than "~1 day" (the demo stub + e2e harness + docs are net-new), but still an M-sized focused PR since the hard part is done. Not on the critical path to either flagship demo (browser connect→approve→revoke, or x402 $5/day) — it is an agent-does-real-DeFi capability expansion. Do it after both flagship demos rehearse.

Scope checklist

• Propose with ProposalOrigin::Agent so Activity attributes swap requests to the agent handle.
• Re-verify sell/buy/receiver rendering through the E5 shared Review (🔴 E5 · The ONE shared Review + honest enforced cap (TRUST-CRITICAL) #185).
• 3 new MCP tools each need a ⌘K command (CLAUDE.md).
• Re-run the PR Swap v1 agent + demo: 3 MCP tools, fork-demo stub, swap-e2e (#26) #69 test matrix: MCP-vs-MockSigner happy path, guardrail-ON behavior, submit-retry idempotency, stub unit tests, swap-e2e env-gated.

Acceptance

1. 11 tools documented consistently; deckard_execute stays tx-only.
2. just demo swap flow completes with the simulated fill + visible "simulated" banner.
3. just swap-e2e produces an accepted+open order on live Sepolia (output pasted in the PR).
4. DoD green; codex adversarial pass.