Add Śrī Yantra · symmetry costs a line

Narrated Manim explainer, 1:08, 1280x720.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01161aC97vUnBnyZRBGyJeHy

README.md

@@ -5,3 +5,4 @@ Narrated Manim maths explainers. Click a `.mp4` to play it in the browser.
 | Video | Length | What it shows |
 | --- | --- | --- |
 | [Śrī Yantra · two poles](yantra-two-poles.mp4) | 2:09 | The Śrī Yantra inverted in its own circle, then lifted onto a sphere: circle inversion becomes a top-to-bottom flip, and the bindu and infinity become the two poles of one sphere. |
+| [Śrī Yantra · symmetry costs a line](yantra-symmetry.mp4) | 1:08 | Forcing up–down mirror symmetry on the yantra while keeping its 29 triple points exact: two bases fuse into one line carrying 1 + 2 points. |