fix: make plugin loadable on OpenClaw 2026.5.7 + wallet funding hint

[KillerQueen-Z]

Three latent bugs that block xclawrouter from loading under OpenClaw 2026.5.7's stricter plugin loader, plus eden's requested wallet-ready funding hint.

Bug A — plugin id mismatch (fatal)

`src/index.ts` declared `id: "clawrouter"` while `openclaw.plugin.json` manifested `"id": "xclawrouter"`. OpenClaw's loader cross-checks them and silently refuses to load on mismatch; only `openclaw plugins doctor` surfaces it:

```
xclawrouter [validation]: plugin id mismatch
(config uses "xclawrouter", export uses "clawrouter")
```

Net effect: gateway boots with "0 plugins" loaded, no provider registered, no proxy on 8402, TUI shows "no models available". Reproduced live this afternoon — was the rename oversight from the `@blockrun/clawrouter` → `xclawrouter` migration.

Bug B — manifest missing `contracts` declarations (fatal)

OpenClaw 2026.5.7 added capability contracts: plugins must declare up front every tool / web-search / image / video / music provider they'll register at runtime. Anything undeclared is dropped and the install itself fails during persist:

```
Config validation failed: tools.web.search.provider:
unknown web_search provider: blockrun-exa

plugin must declare contracts.tools before registering agent tools
```

xclawrouter registers 17 partner tools, blockrun-exa web search, and three media providers — none were declared. OpenClaw rolls the install back, user left with no plugin despite success-looking log lines.

`openclaw.plugin.json` adds a complete `contracts` block listing all 17 tools, `webSearchProviders: ["blockrun-exa"]`, and the three media provider ids. Also augments `OpenClawPluginDefinition` in `src/types.ts` with an optional `contracts` field for completeness.

Bug C — uninstall leaks own plugin entry (minor)

Deactivate path scrubbed legacy `clawrouter` / `@blockrun/xclawrouter` / `XClawRouter` entries from `plugins.entries` but forgot to remove `xclawrouter` itself, so reinstalls accumulated stale records.

Fix: add `"xclawrouter"` to the cleanup key list.

Funding-chain hint (eden's request)

The setup command's success box told users the wallet was ready but didn't say which chain to fund. OKX onchainos only signs x402 on Base today (Solana support hasn't shipped per src/proxy.ts warning), and naming the chain explicitly avoids users bridging to the wrong network. Two lines added to the summary box:

```
│ Fund send USDC on Base to the address above │
│ (free models work at $0; $5 unlocks paid tier) │
```

Why npm 0.12.182 didn't show this

Boss likely tested on an older OpenClaw or via the `curl ... | bash` path with reinstall.sh's `--force` flag. The new validation only fires under OpenClaw 2026.5.7+'s capability-registry path, exercised by `openclaw plugins install` directly (Option 2/3 in README). Once 0.12.182 reaches OpenClaw 2026.5.7 users on those paths, they hit the same bugs we reproduced today.

Test plan

• `openclaw plugins doctor` clean: "No plugin issues detected."
• `openclaw plugins install --force ` succeeds end to end (no rollback)
• Gateway restart loads plugin: log shows `BlockRun provider registered`, `x402 proxy listening on port 8402`
• `curl /v1/models` returns 188 models
• TUI on main agent shows blockrun/* in picker
• Real chat completion routes successfully (`free/gpt-oss-120b` chosen with $0 wallet)
• `npm run typecheck` clean, `npx vitest run src/` passes, prettier clean