v0.7.1 — doc patch: --clip-to-footprint framing

[0.7.1] - 2026-04-12

Documentation-only patch release. No code behavior changes — all
csm2map pipeline outputs are bit-identical to 0.7.0.

Documentation

• Corrected --clip-to-footprint documentation. The flag was
  originally documented as an "ISIS cam2map compatibility mode" that
  matched cam2map by clipping csm2map output to the footprintinit
  polygon. That framing was based on a working hypothesis later
  disproved empirically: ISIS cam2map ignores the polygon entirely
  (stripping the polygon from the cube and re-running cam2map
  produces bit-identical output — see docs/csm2map.qmd § "The footprintinit polygon precision story" for the full narrative).
  All affected documentation has been rewritten to drop the
  cam2map-matching claim and reframe the flag as an escape hatch for
  downstream tooling that explicitly wants a polygon-shaped output
  mask. Affected surfaces:
  • isistools csm2map --help — Typer option help text and
    command docstring no longer claim ISIS-compatibility.
  • docs/csm2map.qmd — Purpose paragraph, Usage example comment,
    options table row, and the former "Pixel-perfect match"
    paragraph rewritten. Cross-references the empirical-disproof
    section.
  • docs/csm2map-design.md §6 Known limitations gains a new
    entry 7 documenting the flag as a historical
    hypothesis-test-reject artifact, flagged as paper-worthy.
  • src/isistools/processing/project.py — clip_to_footprint
    parameter docstring, the in-function console message, and
    the _rasterize_footprint helper docstring all corrected.

Known limitations (unchanged from 0.7.0)

The --clip-to-footprint flag itself is retained in 0.7.1 for
backward compatibility. Deprecation or removal is being considered
for a future release.