TS SDK: delete XComs listed in xcom_keys_to_clear before a task runs - #74220

Follow-up for #74178 (review).

handleTask sends a DeleteXCom for each listed key after it finds the handler and before it binds arguments. This matches the Python task runner, which deletes the listed XComs before it renders templates.

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

• Yes - Claude Code

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