Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)

Generated-by: Claude Code following the guidelines

Before

• Selecting a task + downstream/past/future resolved full set of tasks and cleared everything
• To skip subset of downstream tasks, you had to clear it and retrigger manually

After

• Every affected task instance renders a checkbox, ticking by default
• Per-run granularity with past/future expansions you can keep task X in run 1 while dropping it from run 2

Effect on API

• API calls remain the exact same with no exclusions and lets backend handle set expansion
• With exclusions, UI sends the set as explicit task_ids with expansion flags off

File by File

ActionAccordion/columns.tsx — Adds taskInstanceKey (dag_run_id:task_id:map_index) and a RowSelection type; getColumns now prepends an optional leading checkbox column when selection is passed.

ActionAccordion/ActionAccordion.tsx — Threads the optional selection prop down to the table columns. No change when omitted.

Clear/TaskInstance/ClearTaskInstanceDialog.tsx — Tracks excludedKeys state and wires checkboxes in. On confirm with exclusions, sends the kept instances explicitly, grouped per run with expansion flags off; otherwise unchanged.

Clear/TaskInstance/ClearTaskInstanceConfirmationDialog.tsx — Accepts optional explicit taskIds; when present, the dry-run preview sends those ids with upstream/downstream off so it matches the real clear.

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• For significant user-facing changes create newsfragment: {pr_number}.significant.rst, in airflow-core/newsfragments. You can add this file in a follow-up commit after the PR is created so you know the PR number.