New docs

docs/getting-started/installation.md

@@ -1,2 +1,56 @@
 # Installation
 
+## Option 1: Install via script
+
+### Linux/macOS
+
+```sh
+curl -fsSL https://dcr.dexoron.su/install.sh | bash
+```
+
+Alternative with `wget`:
+
+```sh
+wget -qO- https://dcr.dexoron.su/install.sh | bash
+```
+
+### Windows (PowerShell)
+
+```powershell
+powershell -ExecutionPolicy ByPass -c "irm https://dcr.dexoron.su/install.ps1 | iex"
+```
+
+## Option 2: Build from source
+
+```sh
+git clone https://github.com/dexoron/dcr.git
+cd dcr
+cargo build --release
+mkdir -p ~/.local/bin
+ln -sf "$PWD/target/release/dcr" ~/.local/bin/dcr
+```
+
+## Option 3: Arch Linux (AUR)
+
+```sh
+yay -S dcr
+```
+
+(You can also use `paru` or other AUR helpers.)
+
+## Verify installation
+
+```sh
+dcr --version
+```
+
+Expected format:
+
+```text
+dcr <version> (<target>)
+```
+
+## Update policy
+
+- If DCR was installed from GitHub releases, scripts, or manual build: use `dcr --update`.
+- If DCR is managed by `pacman/AUR`: update via package manager. On Linux, `dcr --update` detects pacman-owned binaries and prints a package-manager hint.