[Bug] Human wallet profile shows 'AI Writer' instead of user's name after OWS linking

[realproject7]

Problem

After linking an OWS wallet via "Link AI Writer", the human wallet's profile shows "AI Writer" + "AI Agent" badge instead of the user's Farcaster name. Root cause: ERC-8004 registration is on the human wallet, creating a two-row DB conflict where getUserFromDB and getAgentUserFromDB return different rows.

Revised approach: ERC-8004 on OWS wallet, DB-only link for human

New architecture

1. ERC-8004 registration goes on the OWS wallet — the agent identity NFT belongs to the wallet that actually signs transactions and publishes stories
2. Human ↔ OWS link is DB-only — plotlink.xyz stores a linked_agent_wallet mapping on the human's user row. No ERC-8004 involvement on the human side
3. Binding proof still required — OWS wallet signs "I authorize {humanWallet} as my owner" to prevent anyone claiming someone else's OWS wallet

Updated flow

Step 1 — plotlink-ows (already exists):
User enters human wallet → OWS wallet signs binding proof → shows code to copy

Step 2 — plotlink.xyz "Link AI Writer":
User pastes OWS wallet address + binding signature → `ecrecover` verifies OWS wallet signed it → DB link created:
```sql
UPDATE users SET linked_agent_wallet = '0xdABF...' WHERE primary_address = '0x4d68...'
```

Step 3 — ERC-8004 registration (plotlink-ows, separate):
OWS wallet registers ITSELF on-chain via ERC-8004 `register()` — no human wallet involved. Uses existing ETH balance (already funded for publishing).

Profile display

• OWS wallet (`0xdABF...`): "AI Writer" + "AI Agent" badge + "Operated by: Project7" (lookup via DB link)
• Human wallet (`0x4d68...`): "Project7" + "Human" badge + "Operates: AI Writer" (lookup via `linked_agent_wallet`)

Benefits

• Human profile never gets agent fields — no two-row DB conflict
• ERC-8004 identity is on the correct wallet (the one that signs txs)
• No `agent_type` distinction needed on human row
• Simpler profile logic: `agentMeta` only returns non-null for actual agent wallets

Migration

• Existing registration (Agent ID 44545 on human wallet) needs to be unregistered and re-registered on OWS wallet
• DB: clear agent fields from human row, add `linked_agent_wallet` column

Implementation tickets (across both repos)

plotlink-ows:

• ERC-8004 self-registration: OWS wallet registers itself (not the human wallet)
• Remove "Generate Wallet Bind Code" step 2 (ERC-8004 setAgentWallet) — no longer needed

plotlink:

• Add `linked_agent_wallet` column to users table
• Update "Link AI Writer" endpoint: verify binding proof → set `linked_agent_wallet` (no ERC-8004)
• Update profile display: use `linked_agent_wallet` for "Operates: AI Writer" on human profiles
• Update WriterIdentity: lookup agent owner via `linked_agent_wallet` reverse lookup
• Migration: clean up existing mis-registered agent data

Files

• `lib/actions.ts` — profile/agent lookup logic
• `src/components/AgentRegister.tsx` — "Link AI Writer" UI
• `src/app/api/user/agent-register/route.ts` — registration endpoint
• `lib/contracts/erc8004.ts` — agent detection
• DB migration for `linked_agent_wallet` column

[realproject7]

Sub-tickets

plotlink-ows

1. plotlink-ows#113 — ERC-8004 self-registration: OWS wallet registers itself
2. plotlink-ows#114 — Remove Step 2 (setAgentWallet) from Settings binding flow

plotlink

3. plotlink#871 — Add linked_agent_wallet column (DB migration)
4. plotlink#872 — Update "Link AI Writer" to DB-only link (no ERC-8004 on human)
5. plotlink#873 — Update profile display to use linked_agent_wallet
6. plotlink#874 — Migration: clean up existing ERC-8004 registration on human wallet

Execution order

#871 (DB column) → #113 (OWS self-register) → #114 (remove step 2) → #872 (link endpoint) → #873 (profile display) → #874 (migration)