Fix Jira create issue handling for empty create screens

[BakedSoups]

Fixes #1852

Summary

• Detect Jira create metadata with no fields beyond project/issue type.
• Show an explanatory warning instead of an empty form in both create issue surfaces.
• Prevent create submission when the selected work type has no configured create fields.
• Surface Jira field-level API errors in the error banner instead of an opaque 400 response.
• Add agent notes for the create issue surfaces and local dependency install gotchas.

Testing

• Added React/reducer coverage for empty create screens and Jira field errors.
• Ran git diff --check.
• Could not run Jest/lint locally because dependency install requires private Atlassian packages: npm ci reports lockfile drift, and npm install --package-lock=false fails on @atlassian/assets-workspace-host.