Support inserting template vars at cursor position; improve RAG preset

[ohltyler]

Description

Mixed-bag PR, includes the following:

• changes the variable insertion in the template from a copy/paste flow, to a single "insert" flow. Cursor position is persisted in the prompt code editor, and when users click "insert" on a particular template var, the formatted var is injected at such position. Further improvements to help automate these things, as well as better & more prompt templates, will come in the future when those flows are finalized and UX feedback is gathered.
• improves the RAG quick-configure presets to follow the new pattern of a model expecting a single 'prompt' field. This is defined in quick create, and used alongside any contextual field (so far, the "text field") and automatically attach as a template variable.'
• improves default transform types for the input / output transforms, and doesn't leave them as empty like before
• minor spacing improvements in the Configure Prompt modal
• NPE check which can be triggered if server-side returns 500s on Workflow List page
• filters out register-agent-related workflows on the Workflow List page
• provides better messaging if resource fetching for a particular workflow (e.g., custom, no ui_metadata found, etc.) when opening the flyout on the Workflow List page

Demo video covering most of the changes listed above:

screen-capture.4.webm

Issues Resolved

N/A

Check List

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[saimedhi]

LGTM

[saimedhi]

LGTM