Fix session logout caused by Jira XSRF filter and credential handling

Fix subtasks block when no subtasks exist yet

Apply code review improvements: memory safety, caching, input validation

Update README to reflect current UI and feature set

Remove per-issue prompt dialog for subtasks

Add subtasks prompt editor to Options page

Fix sidebar panel position: use confirmed Agil module selector

Move AI buttons to right sidebar panel below 'Agil' module

Fix invalid CSS selector for numeric custom field IDs

Fix four issues found during testing

Initial implementation: Jira LLM Assistant Chrome Extension