docs(plan): add custom scan pipeline implementation plan 7 tasks: PerspectiveTransformer (TDD), ImageFilters (TDD), CornerOverlayView, EditorActivity, CameraX CameraActivity, home rewire + ML Kit scanner removal, finalize+deploy. Full code per step. Constraint: pure Android (no native libs); CAMERA permission added. Confidence: high Scope-risk: module Reversibility: moderate Directive: execute via subagent-driven-development. Tested: plan self-review. Not-tested: no code yet. Related: 2026-05-31-clearcam-custom-scan-pipeline-design.md 🐙 Autopus