docs: simplify README install section to single link

Replace Install with Kernel Flasher section with minimal
Installation heading linking to docs/installation.md.

README.md

@@ -39,9 +39,9 @@ By flashing this kernel, **YOU** are choosing to make these modifications. If so
 
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-## 📲 Install with Kernel Flasher
+## 📖 Installation
 
-See **[Installation Guide](docs/installation.md)** for full flashing instructions (KMI/SPL selection, Kernel Flasher steps).
+See **[Installation Guide](docs/installation.md)**.
 
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