[Feature] Redesign Link AI Writer flow: fetch tokenURI first, pre-fill agent data

[realproject7]

Context

The current Link AI Writer flow requires 3 manual inputs (OWS wallet, binding signature, agent ID) and the DB row ends up with `agent_name = null` because RPC metadata lookups fail. This redesign fetches agent data upfront via `tokenURI` and pre-fills the form.

New Flow

Step 1: Enter OWS Wallet Address

User enters the OWS wallet address. Frontend calls a lookup endpoint.

Step 2: Fetch & Display Agent Info

Backend fetches the agent data via RPC:

1. `balanceOf(owsWallet)` — confirm wallet owns an agent NFT
2. `tokenOfOwnerByIndex(owsWallet, 0)` — get agent ID (may fail, handle gracefully)
3. `tokenURI(agentId)` — get full metadata JSON

If `tokenOfOwnerByIndex` fails (not enumerable), try:

• `ownerOf(id)` for a range of recent IDs (costly, skip for now)
• Or let user manually enter agent ID, then verify with `ownerOf` + `tokenURI`

Display the agent info to the user:
```
Found: P7 AI Writer
Agent ID: 45557
Description: AI fiction co-writer operated by Project7...
Genre: Romance, Sci-Fi
```

Pre-fill Agent ID so user doesn't need to type it.

Step 3: Paste Binding Signature

User pastes the binding signature from plotlink-ows. Only this one field — OWS wallet and agent ID are already filled.

Step 4: Sign & Link

Same as current: human wallet signs, API verifies both signatures, creates DB row with ALL agent data from the tokenURI.

API Changes

New: `GET /api/user/lookup-agent?wallet=0x...`

Looks up an OWS wallet's agent data via RPC:

```json
{
"found": true,
"agentId": 45557,
"name": "P7 AI Writer",
"description": "AI fiction co-writer...",
"genre": "Romance, Sci-Fi",
"llmModel": "Claude",
"registeredAt": "2026-04-24T..."
}
```

Uses `tokenURI` (ERC-721 standard) — NOT `agentURI` which reverts on this contract.

Update: `POST /api/user/link-agent`

Accept full agent metadata in body:
```json
{
"humanWallet": "0x...",
"owsWallet": "0x...",
"signature": "0x...",
"humanSignature": "0x...",
"agentId": 45557,
"agentName": "P7 AI Writer",
"agentDescription": "...",
"agentGenre": "Romance, Sci-Fi"
}
```

No RPC calls during linking — all data comes from the frontend (pre-fetched in step 2).

Frontend Changes

`src/components/AgentRegister.tsx` — LinkAIWriter component

Redesign to multi-step:

1. Input: OWS Wallet Address → [Lookup] button
2. Display: Agent info card (name, ID, description) — auto-filled from lookup
3. Input: Binding Signature (single paste field)
4. Button: Link AI Writer → sends all data

```
┌─────────────────────────────────────────────────────┐
│ Link AI Writer (PlotLink OWS App) │
│ │
│ OWS Wallet Address: │
│ [0xdABF...d3D1 ] [Lookup] │
│ │
│ ┌─────────────────────────────────────────────────┐ │
│ │ ✓ Found: P7 AI Writer │ │
│ │ Agent ID: 45557 │ │
│ │ Genre: Romance, Sci-Fi │ │
│ └─────────────────────────────────────────────────┘ │
│ │
│ Binding Signature: │
│ [0x14d340... ] │
│ │
│ [Link AI Writer] │
└─────────────────────────────────────────────────────┘
```

Sync with Direct Registration (Flow B)

The direct registration flow (`AgentRegister` component, "Register New AI Agent") already creates the DB row with all fields because the form data is available. No changes needed there — it uses `agent_type = 'direct'` and the connected wallet IS the agent.

Ensure both flows create consistent DB records:

Field	OWS Writer (Flow A)	Direct (Flow B)
agent_type	ows-writer	direct
agent_id	from tokenURI lookup	from register() tx
agent_name	from tokenURI	from form
agent_wallet	owsWallet	connected wallet
agent_owner	humanWallet	connected wallet

Important: Use `tokenURI` not `agentURI`

The ERC-8004 contract stores metadata via `tokenURI` (ERC-721 standard), NOT `agentURI`. The existing `getAgentMetadataById` in `lib/contracts/erc8004.ts` uses `agentURI` which reverts. Must be updated to use `tokenURI`.

Files

• `src/app/api/user/lookup-agent/route.ts` — new endpoint
• `src/app/api/user/link-agent/route.ts` — accept full metadata, remove RPC calls
• `src/components/AgentRegister.tsx` — redesign LinkAIWriter to multi-step with lookup
• `lib/contracts/erc8004.ts` — fix `getAgentMetadataById` to use `tokenURI`

Acceptance Criteria

• Entering OWS wallet + clicking Lookup shows agent info card
• Agent ID pre-filled from lookup (user doesn't type it)
• Agent name/description populated in DB after linking
• Only binding signature needs manual paste
• No RPC calls during the linking step (all data pre-fetched)
• Profile shows correct agent name after linking
• `tokenURI` used instead of `agentURI` in erc8004.ts
• Direct registration flow unchanged and consistent

---

Important: Use shared RPC client with retry fallback

The new lookup endpoint and any RPC calls must use the shared publicClient from lib/rpc.ts — NOT create a new createPublicClient instance. The shared client has retry logic across multiple public RPC endpoints (publicnode, mainnet.base.org, drpc, llamarpc) which significantly reduces rate limit failures.

import { publicClient } from '../../../../lib/rpc';
// NOT: const publicClient = createPublicClient({ ... });