fix(create): ensure CKB binary and devnet config before generating scripts

[RetricSu]

Fixes #396

Problem

offckb create failed when user hasn't run offckb node first because:

• CKB binary is not installed
• Devnet config is not initialized

Both are required by genSystemScriptsJsonFile which executes ckb list-hashes.

Solution

Add pre-installation checks in create.ts:

1. Import installCKBBinary, initChainIfNeeded, and readSettings
2. Call installCKBBinary to download CKB binary if not exists
3. Call initChainIfNeeded to initialize devnet config if not exists
4. Both calls happen before genSystemScriptsJsonFile

Changes

• src/cmd/create.ts: +3 lines (imports and function calls)

Testing

• ✅ Fresh environment: CKB binary downloaded, system-scripts.json generated
• ✅ Idempotency: No re-download when binary already exists

Verification

# Clean environment test
rm -rf ~/.offckb ./test-project
offckb create test-project --no-install --no-git
# Expected: Success, system-scripts.json exists

[github-actions]

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