feat(grpc-web): browser client at @sentrix/chain/grpc-web

[satyakwok]

Summary

Adds the grpc-web subpath — browser-side equivalent of the Node-only `/grpc` client. Same surface (`GrpcWebClient` mirrors `GrpcClient` method names), same chain endpoint (`grpc.sentrixchain.com:443`). Caddy at the edge transcodes gRPC-Web ↔ native gRPC via `tonic-web`, so server code is identical and dApp code that reads from both rails (eg an Electron app + a CLI sharing a UI lib) doesn't need to branch per environment.

Implementation

• `@protobuf-ts/grpcweb-transport` for the wire layer
• Generated TS stubs (`sentrix.ts` + `sentrix.client.ts`) committed under `src/grpc-web/` via `@protobuf-ts/plugin` so consumers don't need `protoc` installed
• Regenerate via:
  ```
  npx protoc --ts_out=src/grpc-web --proto_path=src/grpc-proto src/grpc-proto/sentrix.proto
  ```

Available calls (chain v0.4+)

Method	Returns
`getLatestBlock()` / `getBlockByHeight(h)`	`Block`
`getBalance(address)`	`Account` (20-byte hex or Uint8Array)
`getValidatorSet({ atHeight? })`	`ValidatorSet`
`getSupply({ atHeight? })`	`Supply`
`getMempool({ limit })`	`Mempool`
`streamEvents([filters])`	async iterable of `ChainEvent`

Usage

```ts
import { GrpcWebClient } from "@sentrix/chain/grpc-web";

const c = new GrpcWebClient("mainnet");
const block = await c.getLatestBlock();

for await (const ev of c.streamEvents([])) {
console.log(ev);
}
```

Verification

End-to-end via Node fetch (same transport as browser):
`mainnet latest: { index: '1679486', txs: 0 }`

Cross-rail symmetry

SDK now has a node + browser door for every read surface:

Surface	Node	Browser
EVM	`/evm` (viem)	`/evm` (viem)
REST	`/native`	`/native`
WebSocket	`/bft`	`/bft` (works in browser via native WebSocket)
gRPC	`/grpc` (@grpc/grpc-js)	`/grpc-web` (@protobuf-ts/grpcweb-transport)
Wallet	`/wallet`	`/wallet`