chore: sweep mosaicstack/mosaic-stack → mosaicstack/stack + add short install URL

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

README.md

@@ -6,6 +6,12 @@ Mosaic gives you a unified launcher for Claude Code, Codex, OpenCode, and Pi —
 
 ## Quick Install
 
+```bash
+curl -fsSL https://mosaicstack.dev/install.sh | bash
+```
+
+Or use the direct URL:
+
 ```bash
 bash <(curl -fsSL https://git.mosaicstack.dev/mosaicstack/stack/raw/branch/main/tools/install.sh)
 ```
@@ -301,6 +307,12 @@ Each stage has a dispatch mode (`exec` for research/review, `yolo` for coding),
 
 Run the installer again — it handles upgrades automatically:
 
+```bash
+curl -fsSL https://mosaicstack.dev/install.sh | bash
+```
+
+Or use the direct URL:
+
 ```bash
 bash <(curl -fsSL https://git.mosaicstack.dev/mosaicstack/stack/raw/branch/main/tools/install.sh)
 ```