fix(iterate): require decimal interval values

[aiirvizionz]

Summary

• Rejects non-decimal JavaScript numeric forms such as 1e2 and 0x10 for iterate interval values
• Keeps positive safe integer interval parsing for plain decimal inputs
• Adds regression coverage to the existing iterate option parser tests

Verification

• node_modules/.bin/vitest.CMD run packages/cli/src/commands/iterate.test.ts
• node_modules/.bin/tsc.CMD -p packages/cli/tsconfig.json --noEmit
• git diff --check