docs(readme): replace rock logo with light mark

.omo/evidence/20260809-readme-light-logo/qa.md

@@ -0,0 +1,35 @@
+# README Light Logo QA
+
+## What was tested
+
+- Compared `.github/assets/omo-icon-light.svg` with the source asset from
+  `sisyphuslabs-web/public/assets/omo-icon-light.svg` using SHA-256.
+- Parsed the committed SVG with `xmllint --noout`.
+- Confirmed the root `README.md` references the tracked
+  `.github/assets/omo-icon-light.svg` file.
+- Rendered the committed SVG through macOS Quick Look at 512 px and inspected
+  the resulting PNG.
+
+## What was observed
+
+- Source and committed SHA-256:
+  `0cb99c9fc750827f2c35ae99659de6d40e03ae7b1d79d3c29f1002017fe33b0a`.
+- XML parsing completed without errors.
+- The root README image path resolves to the tracked light SVG.
+- The rendered image was 512 x 512 with alpha and visibly showed the intended
+  dark OmO cat mark on the light rounded-square background, with no clipping or
+  malformed paths.
+- Manual render artifact during QA:
+  `/tmp/omo-light-logo-qa/omo-icon-light.svg.png`.
+
+## Why it is enough
+
+The exact source hash proves the committed file is the requested light asset.
+Parsing and path-resolution checks cover broken-file and broken-link risks.
+The rendered image inspection covers the user-visible README logo surface.
+
+## What was omitted
+
+- The temporary rendered PNG is not committed because it is a derived QA
+  artifact and the source SVG is the shipped asset.
+- No credentials, environment dumps, or private logs were captured.

README.md

@@ -1,5 +1,5 @@
 <div align="center">
-  <img src=".github/assets/lazycodex-logo.png" alt="LazyCodex" width="280">
+  <img src=".github/assets/omo-icon-light.svg" alt="LazyCodex" width="280">
 
   <h1>LazyCodex</h1>