cleanup: remove test_adaptive_fps.sh one-time validation script (#1376)

Remove test script that served its purpose validating adaptive FPS
calculations during feature development. The script was created on
Oct 9, 2025 (#1349) to validate logic before implementation and is
no longer needed.

## Rationale

**One-time validation**: Created to test FPS calculations across
various video durations (3s to 1 hour) during development.

**Zero integration**: Not referenced in extract-best-frame procedure
or any other scripts. No external dependencies.

**Logic documented**: The adaptive FPS calculations are now documented
in the extract-best-frame-procedure.md itself (lines 79-103).

**Served its purpose**: Successfully validated the logic, feature
merged and working.

## Additional Cleanup Notes

**./~ directory**: Empty artifact directory (~/ppv/pillars/) found in
root but not tracked by git - removed manually, not part of this commit.

**docs/ links verified**: All knowledge/ procedure references to
detailed docs/ files are valid and functional.

Related to #1349 (adaptive FPS feature)

Principle: subtraction-creates-value

Author: atxtechbro