docs(runtime): align README with current runtime packages

[Iam-Karan-Suresh]

This PR updates the runtime README to reflect the current state of the pkg/runtime packages.

Changes include:

• Aligning the runtime configuration options with existing packages and correcting outdated references.
• Fixing package naming inconsistencies (e.g. jiter).
• Adding documentation for reconciliation helpers to clarify how reconcile results integrate with patching.
• Documenting runtime-facing packages that were previously undocumented to reduce future documentation drift.

This aims to ensure the README accurately represents the runtime APIs available to controller authors and contributors.

issue: #263