refactor(wallet): delegate resolution to @blockrun/core

[KillerQueen-Z]

What

Makes @blockrun/llm the first shared SDK consumer of @blockrun/core.

• Adds @blockrun/core@^0.0.3.
• Delegates provider-wallet scanning, file resolution, environment precedence,
  getOrCreateWallet, and getWalletAddress to the shared kernel.
• Keeps the SDK's public function names and wallet-creation/funding behavior
  unchanged.
• Adds characterization coverage for the canonical resolution order:
  env → provider wallet.json → ~/.blockrun/.session → legacy wallet.key.

Why

Franklin and MCP already consume this SDK. Once this merges, their wallet
resolution automatically shares the same source of truth as the official
blockrun CLI and clawrouter-codex, without any forced migration for users.

Lockfile note

package-lock.json is regenerated because the upstream lockfile's root package
metadata was already behind the current package.json. The large lockfile diff
aligns it with the declared dependency versions and adds the published core
package; it does not alter the SDK API surface.

Validation

• npm run build — passed.
• HOME=/tmp/blockrun-llm-test-home npm test — 200 passed, 12 production
  integration tests skipped by design, TypeScript type checks passed.
• New wallet characterization tests: 3 passed.