compass sprint charts –output-dir is ignored by the gnuplot render step

compass sprint charts --output-dir <dir> advertises a general output location override, and its Python data-prep step honours it (writes sprint_activity.csv, sprint_progress.csv, pr_cycle_times.csv into <dir>). But the four tangled gnuplot scripts under scripts/ (sprint_prs_commits.gnuplot, sprint_line_churn.gnuplot, sprint_pr_cycle.gnuplot, sprint_stories_done.gnuplot, all tangled from doc/agile/sprint_charts.org) each hardcode both their CSV input path (build/output/sprint_%s/sprint_activity.csv, printf-formatted from the sprint number alone) and their PNG set output path (doc/agile/versions/v0/sprint_%s/<name>.png) — neither honours --output-dir at all. Reproduced this session: ran compass sprint charts --sprint 22 --output-dir doc/agile/versions/v0/sprint_22, which happened to still find a stale build/output/sprint_22/sprint_activity.csv left over from an earlier run (5 days of data, cut off at 2026-07-05, with a spurious 2026-06-30 row) and silently rendered all four charts from it — 4 days short of the sprint's actual 9 days of activity. The bug was only caught because the charts visibly stopped mid-sprint; a same-day regeneration for the default output dir would have masked it entirely by coincidence.

Silent stale-data rendering is worse than an outright failure: the charts looked plausible (axes, legend, and styling all correct) and would have shipped into the sprint's health-review record showing 4 days of activity instead of 9, understating both commit load and PR velocity right when a health review most needs accurate numbers. The --output-dir flag's own --help text promises a general override with no caveat that only half the pipeline respects it.

• scripts/sprint_prs_commits.gnuplot, scripts/sprint_line_churn.gnuplot, scripts/sprint_pr_cycle.gnuplot, scripts/sprint_stories_done.gnuplot — all four hardcode build/output/sprint_%s/ as the CSV read path and doc/agile/versions/v0/sprint_%s/ as the PNG write path.
• doc/agile/sprint_charts.org — literate source these scripts tangle from; the fix belongs there, then re-tangle.
• Reproduced 2026-07-10 on sprint 22: stale build/output/sprint_22/sprint_activity.csv (5 rows, last day 2026-07-05) silently used instead of the fresh 9-row CSV written to doc/agile/versions/v0/sprint_22/ by the same invocation.