Feature: add hardened schema helpers for agent-safe CLIs

[alleneubank]

One thing that worked well in our fork was adding first-class hardened schema helpers plus default control-character rejection for parsed strings.

The goal was to make agent-facing CLIs safer by default without requiring every command author to rediscover the same validation patterns.

The patch adds helpers like:

• hardened.path()
• hardened.id()
• hardened.text()
• hardened.url()

It also makes parser-handled z.string() inputs reject ASCII control characters by default, with an explicit opt-out via schema metadata.

That gave us:

• safer path handling
• safer free-form text handling
• safer URL/id handling
• parser-wide protection instead of per-command ad hoc checks

Reference patch:

• alleneubank/incur@4bd013b

Example from the patch:

if (typeof value !== 'string' || allowsControlChars(schema) || !hasControlChars(value)) return []

Would you be interested in upstreaming hardened input primitives like this, either as built-ins or as an optional companion export?