Fix three issues: init __what_to_create, honor resample_dt, and correct get_t_isco indexing

[AnujKankani]

Motivation

• set_initial_time referenced self.__what_to_create before it was initialized, which can raise an AttributeError if initial time is set prior to selecting what to create.
• The CCE initialization routine accepted a resample_dt argument but did not apply it, causing callers to be ignored.
• get_t_isco computed a nearest-frequency index from a cropped frequency array but indexed the uncropped time array, producing incorrect ISCO time lookups.

Description

• Initialize self.__what_to_create = "Nothing" in the BOB.__init__ constructor to ensure the attribute exists before set_initial_time uses it.
• Set self.resample_dt = resample_dt at the start of the CCE initialization function so the passed resample_dt is honored for resampling.
• Replace indexing of self.data.t[...] with freq_data.t[...] in get_t_isco so the time lookup matches the cropped frequency array used to compute the index.

Testing

• Executed automated edit-and-verify scripts that applied the three minimal changes and read back gwBOB/BOB_utils.py to confirm the intended lines were modified, and those checks passed.
• No project unit test suite (e.g. pytest) was executed for these changes.
• Performed static inspection of the modified lines to confirm each fix is a single-line, localized change and no other behavior was altered.

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Codex Task