Support --map-index in airflowctl tasks state

[IamJasonBian]

Stacked on top of #66202 — opening as a draft so the follow-up is visible while #66202 is still in review.

Addresses @parkhojeong's CHANGES_REQUESTED feedback on #66202: the new airflowctl tasks state command currently can't query a mapped task instance, so it doesn't match legacy airflow tasks state --map-index. The Airflow REST API exposes a separate path-parameter endpoint for mapped instances:

• unmapped: GET /api/v2/dags/{dag_id}/dagRuns/{dag_run_id}/taskInstances/{task_id}
• mapped:   GET /api/v2/dags/{dag_id}/dagRuns/{dag_run_id}/taskInstances/{task_id}/{map_index}

Hitting the unmapped endpoint for a mapped TI returns a 404 with the message "Task instance is mapped, add the map_index value to the URL", so today the command just hard-fails on any mapped task.

Changes (top commit only — 7156ab6)

• TaskInstancesOperations.get now accepts an optional map_index and routes to the mapped endpoint when it's non-negative. Sentinel uses the existing int = None # type: ignore pattern from XComOperations so the auto-generated taskinstances get command continues to work when the flag is omitted.
• New --map-index flag on airflowctl tasks state (default -1, matching legacy airflow tasks state semantics).
• Three new parametrized unit tests for the mapped path (map_index ∈ {0, 1, 7}); existing unmapped tests untouched.
• The auto-generated taskinstances get command also gains optional --map-index support transparently.

Stacking note

The bottom two commits in this branch (cfdb6617, f1e90629) belong to @hyungryuk from #66202 — they're only here because #66202 hasn't merged yet. Once #66202 lands, this PR will rebase to the single 7156ab6 commit (52 +/3 - across 4 files) and come out of draft.

If @hyungryuk would prefer to fold the map-index support directly into #66202 instead of landing it as a follow-up, I'm happy to close this and push the diff there as a suggested change.

related: #66174
follows: #66202

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

• Yes — Claude Code (Opus 4.7)

Generated-by: Claude Code (Opus 4.7) following the guidelines

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[hyungryuk]

@IamJasonBian Thanks! I’ve merged your suggested changes into my PR. The branch is now updated with the additional commits. (d76a2fc)

[potiuk]

@IamJasonBian A few things need addressing before review — see our Pull Request quality criteria.

• ❌ Pre-commit / static checks — Failing: CI image checks / Build documentation (--spellcheck-only). The PR likely introduces a word the spellchecker doesn't recognize — add it to docs/spelling_wordlist.txt (alphabetical order) or rephrase. See docs.

No rush.

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Note: This comment was drafted by an AI-assisted triage tool and may contain mistakes. Once you have addressed the points above, an Apache Airflow maintainer — a real person — will take the next look at your PR. We use this two-stage triage process so that our maintainers' limited time is spent where it matters most: the conversation with you.

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Drafted-by: Claude Code (Opus 4.7); reviewed by @potiuk before posting

[IamJasonBian]

@potiuk thanks! - added to docs/spelling_wordlist.txt‎ and rebased