SDD: Add extensionPath logic to unblock style guide, workflow, etc artifact retrieval.

[mahimashanware]

Description:
This issue tracks the addition of support for the ${extensionPath} variable in extension TOML commands to enable portability.

Currently, extension commands lack a reliable way to reference bundled files or assets (like the templates folder in Conductor) without hardcoding absolute paths or relying on fragile installation assumptions.

Goals:

1. Enable dynamic injection of an ${extensionPath} variable in extension command prompts to allow referencing internal assets without hardcoded paths.
2. Update built-in extensions to utilize this new variable, ensuring reliable access to bundled resources across different installation environments.