Report writing utility file

[kyle-hoffmeyer]

Summary

This PR creates a report writing utility file and creates utility functions for exporting dataframes to csvs/excel files.

Every report generator in TraceLens/Reporting/ ended with its own copy of the same "write these DataFrames out" boilerplate: make the CSV directory, loop and write one CSV per sheet, check that openpyxl is importable, open an ExcelWriter, and loop again writing one sheet per DataFrame. Ten generators carried a near-identical version of this block — roughly 300 lines of duplicated logic.

Because each copy drifted independently, they had also become inconsistent in ways that were quietly buggy:

• Sheet-name truncation. Excel caps sheet names at 31 characters. Some generators truncated with a bare [:31] (which silently collides when two long names share a prefix), some did collision-safe truncation, and several did no truncation at all — meaning a long sheet name would make the whole report fail.
• Missing-openpyxl handling. Half the generators prompted the user to pip install openpyxl; the other half raised ImportError; a couple didn't check at all. openpyxl is in fact a declared install dependency, so all of this was dead defensive code.
• CSV vs. Excel exclusivity. Some generators wrote both CSV and Excel when both output paths were given; five others silently suppressed the Excel output the moment a CSV directory was supplied.

This PR consolidates all of that into a single shared utility and migrates every generator onto it, which both removes the duplication and makes the behavior uniform.

Implementation

New write_report_outputs() in TraceLens/Reporting/reporting_utils.py. This is the one place report DataFrames get written. It takes the {sheet_name: DataFrame} mapping plus optional xlsx_path and csvs_dir, and writes whichever outputs were requested (both, if both are given). Two smaller behaviors are folded in:

• hide_columns — an optional {sheet_name: [column, ...]} mapping for columns that should be hidden in the Excel view (they stay in the file, just collapsed). This exists so the comparison report, the one generator that post-processes its worksheets, can express its column-hiding declaratively instead of reaching into the writer itself.
• skip_empty — drops None/empty DataFrames from all outputs. Off by default (an empty-but-present sheet is often a meaningful "we looked and found nothing" signal), opted into only by the genesis report.

Sheet-name sanitization is handled once, in the new _safe_sheet_name() helper (promoted from the genesis report, which already had the only collision-safe implementation): truncate to 31 chars, and if the name of the sheet already exists append _1, _2, ... to the end of the name while staying within the 31 char limit.

New derive_pftrace_output_path() in TraceLens/Reporting/pftrace_utils.py. The three pftrace generators each had an identical block for turning an input trace path into a default .xlsx path (stripping .pftrace / .json.gz / other suffixes). That block is now a single helper parameterized by the report-specific suffix.

Tests

• Added TestWriteReportOutputs, TestSafeSheetName, and TestDerivePftraceOutputPath to tests/test_reporting_utils.py (18 cases). Coverage includes CSV-only, Excel-only, and both-at-once output; the no-op case; long-name truncation and dedup; skip_empty behavior in both directions; hide_columns hiding the right column while leaving the data intact and ignoring column names that don't exist; and a regression test for the "sheet"-name collision described above.
• Moved the sheet-name tests out of tests/test_genesis.py (where they imported the helper from the genesis module) into tests/test_reporting_utils.py, so they now live next to the function's actual home.
• Ran the affected generators' existing suites (genesis, comparison, rocprof, pftrace memory-copy) to confirm the migration and the both-outputs behavior change don't regress them.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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