Week 6: tighten slide 3 panel widths and slide 6 boomerang arrow

Mirrors agent-presentation commit 52cf02a. Slide 3 agent-agnostic trio
SVG now sizes each card to its screenshot's natural aspect ratio so
Claude Code and Codex CLI panels are wider (not square-cropped),
giving all three runtimes equal visual weight. Slide 6 grant-pipeline
boomerang re-anchors to cardinal points on the Self-review and Aims
circles with a clean down-pointing arrowhead.

Author: neuromechanist