Add TODO.md integration to TODOs panel

- Parse TODO.md markdown checkboxes and display in collapsible section
- Add ProjectTodoItem model for TODO.md items with section/subsection support
- Swap context panel tab order to: Jira, TODOs, Problems
- Add "Create TODO.md" button when file doesn't exist with template
- Click project TODO items to navigate to TODO.md at that line
- Add header to TODO.md explaining Clide integration format
- Add pre-commit config with ruff linting and formatting
- Update ruff ignore rules for Textual patterns

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

TODO.md

@@ -1,5 +1,18 @@
 # TODO
 
+<!--
+  Clide Integration: This file is parsed by Clide's TODO panel.
+
+  Format:
+  - Use ## for sections and ### for subsections
+  - Use markdown checkboxes: - [ ] for open items, - [x] for completed
+  - Items appear in the TODOs panel grouped by section
+  - Click an item in Clide to jump to this file at that line
+
+  For AI agents: Add new items under the appropriate section using the
+  checkbox format. Mark items as done with [x] when completed.
+-->
+
 Long-term open items for Clide development.
 
 ## Core Features