feat: add /history command

[natureloved]

What this changes

Closes #3.

Adds a read-only /history command that fetches recent smart-account transactions from MonadScan, including internal transactions, and displays the direction, MON amount, transaction hash, and explorer link.

How I tested it

• npm run build succeeds
• npm run smoke prints SMOKE_OK
• Ran the REPL and exercised the change
• Dry-run send
• Real gasless send (paste the tx hash if so):

Additional focused tests:

• node --test test/history.test.mjs — 7 tests passed
• JavaScript syntax checks passed

Build and smoke testing were not completed in this Windows environment because of the existing clone/workspace setup and missing runtime wallet/model configuration.

Model / platform tested on:

Windows, Node.js 24.16.0. History normalization and mocked explorer API behavior were tested without a live wallet.

Scope check

• This stays within v0 scope (native MON, single account, testnet), OR
• This grows the scope, and I've described the new surface above.

Conventions

• I used npm (not pnpm/yarn) and did not add a global sodium-native override.
• I did not commit .env, seeds, keys, or model weights.

[portdeveloper]

lgtm, thanks