Svelte 5: `derived` type is not overloaded

[huntabyte]

Describe the bug

In Svelte 5, the derived type isn't overloaded like it is in Svelte 4, causing the value to be typed as any.

Reproduction

const a = writable(false)
const b = derived(a, aVal => {
	// aVal is of type `any`
})

Logs

No response

System Info

System:
    OS: macOS 14.2
    CPU: (12) arm64 Apple M2 Max
    Memory: 187.48 MB / 32.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 18.16.0 - ~/.nvm/versions/node/v18.16.0/bin/node
    npm: 9.5.1 - ~/.nvm/versions/node/v18.16.0/bin/npm
    pnpm: 8.10.2 - ~/.nvm/versions/node/v18.16.0/bin/pnpm
    bun: 1.0.3 - ~/.bun/bin/bun
  Browsers:
    Edge: 120.0.2210.61
    Safari: 17.2
  npmPackages:
    svelte: ^5.0.0-next.1 => 5.0.0-next.22

Severity

blocking an upgrade