Preserve significant whitespace in replay and session script serialization

[thymikee]

Overview

PR #364 fixes replay and session context-header escaping by switching to full JSON string serialization for device labels. The remaining script formatting helpers still trim many argument values before serializing them.

Follow-up

• Define which commands should preserve leading and trailing whitespace exactly and which should normalize it.
• Audit formatScriptArg and formatScriptArgQuoteIfNeeded with that contract in mind.
• Consolidate script serialization around a single round-trip-safe encoding rule where practical.
• Add regression coverage for leading spaces, trailing spaces, tabs, and empty-string arguments in replay and session files.

Why this is worth tracking

This would make replay semantics more robust, reduce hidden assumptions in script plumbing, and avoid future one-off escaping or normalization fixes.

Reference

• PR fix: harden command execution and replay script escaping #364