feat(adapter-midnight): Auto-generate Private State ID for improved UX

[pasevin]

Summary

When loading a Midnight contract, users are currently required to manually input a Private State ID - a field that most users don't understand and shouldn't need to worry about. This creates unnecessary friction in the onboarding flow.

Problem

• Users ask: "What should I put in the Private State ID field?"
• The field is an implementation detail that doesn't provide value to end users
• Manual input increases cognitive load and potential for errors

Proposed Solution

Auto-generate the Private State ID deterministically based on the contract address and wallet address:

// Generate a deterministic ID from contract + wallet
const privateStateId = generateDeterministicId(contractAddress, walletAddress);
// e.g., hash or concatenation like: `${contractAddress}_${walletAddress.slice(-8)}`

Benefits

1. Reduced cognitive load - Users don't need to understand this implementation detail
2. Fewer errors - No typos, no accidentally reusing IDs
3. Smoother onboarding - One less required field
4. Automatic state restoration - Same user + same contract = same private state (deterministic)

Implementation Notes

• Remove privateStateId from getContractDefinitionInputs() in the Midnight adapter
• Generate the ID internally when loading/interacting with contracts
• The ID should be deterministic so private state is automatically restored across sessions
• Consider displaying the generated ID in the contract info panel for transparency

Files to Modify

• packages/adapter-midnight/src/adapter.ts - Remove field from getContractDefinitionInputs()
• Transaction/contract loading logic - Add deterministic ID generation

Context

This improvement was identified from user feedback asking what to put in the Private State ID field.