UI: Keep Grid visible on the DAG run page by moving Graph to a tab

[anushkagupta200615-jpg]

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This PR addresses the user feedback regarding the layout in Airflow 3 where the Grid and Graph views were mutually exclusive in the left panel, causing users to lose context when navigating between them.
To improve the UX and keep the Grid visible at all times, we have implemented Option A: The Graph view has been decoupled from the left panel and moved to the right details panel as a permanent tab.
Changes made:

• Added a new Graph tab and routing for both the DAG-level (dags/:dagId/graph) and DAG Run-level (dags/:dagId/runs/:runId/graph).
• Removed Graph from the left panel toggle (dagViewOptions) inside PanelButtons.tsx, meaning the main panel is now strictly reserved for Grid and Gantt views.
• Removed all dead conditional rendering logic tied to dagView === "graph".
• Gracefully reset user's local storage dagView to grid if they previously had graph saved.
• Extracted Graph-specific settings (Dependencies and Direction) from PanelButtons.tsx into a new <GraphSettings /> popover, which is now rendered directly over the React Flow map in the Graph tab alongside <GraphTaskFilters />.
  closes: UI: Keep Grid visible on the DAG run page, or let users pick their own layout #67472

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