feat: add download mirrors and drop legacy install scripts

Introduce `--mirror` and `DCRUP_MIRROR` so `dcrup` can fetch prebuilt
binaries from multiple CDNs. Default `auto` tries cf → gh → sf → ya
and uses the first successful download.

- dcrup.sh / dcrup.ps1: mirror chain, CLI flag, env override
- remove install.sh / install.ps1 / install_bsd.sh (superseded by dcrup)
- GitHub Actions: upload releases to Cloudflare R2 next to Yandex S3
- docs: README, FAQ, changelog, installation, env vars, contributing

docs/README.mdx

@@ -11,7 +11,8 @@ sidebar_label: Introduction
 # Installation (dcrup)
 curl -fsSL https://sh.dcr-tool.ru | sh -s -- self-install
 export PATH="$HOME/.dcr/bin:$PATH"
-dcrup install stable
+dcrup install stable                 # auto: cf → gh → sf → ya
+# dcrup install stable --mirror cf   # CloudFlare / GitHub / SourceForge / Yandex
 
 # Create a project
 dcr new my-app

docs/changelog.mdx

@@ -4,6 +4,12 @@ sidebar_label: Changelog
 
 # Changelog
 
+## Unreleased
+
+- **Download mirrors in `dcrup`** — `--mirror auto|cf|gh|sf|ya` and `DCRUP_MIRROR`.
+  Default `auto` tries **cf → gh → sf → ya** (CloudFlare CDN, GitHub, SourceForge, Yandex CDN).
+- **Removed `install.sh` / `install.ps1` / `install_bsd.sh`** — superseded by `dcrup`.
+
 ## 0.8.5 (2026-08-08)
 
 - **`package.dcr-version`** — optional CLI version pin in `dcr.toml`.

docs/contributing.mdx

@@ -8,6 +8,7 @@ sidebar_label: Contributing
 
 ```bash
 git clone https://github.com/dexoron/dcr
+# or a source mirror: GitVerse / SourceCraft / SourceForge / GitLab (see README)
 cd dcr
 cargo build
 ```

docs/faq.mdx

@@ -61,6 +61,15 @@ Use `kind = "flat-bin"` (NASM `-f bin`) and optional `[archive]` for a FAT disk
 
 See [OS-dev recipe](/docs/recipes/os-flat-bin-archive).
 
+## How do I choose a download mirror?
+
+`dcrup install` uses `--mirror auto` by default and tries **cf → gh → sf → ya**.
+
+```bash
+dcrup install stable --mirror cf
+export DCRUP_MIRROR=ya
+```
+
 ## Lock file
 
 `dcr.lock` is created during builds (`dcr build`) when registry dependencies are present. To force an update — delete `dcr.lock` and run `dcr build`.

docs/getting-started/installation.mdx

@@ -45,10 +45,12 @@ After `self-install`, the command is **`dcrup`** (no `.sh` / `.ps1`): shims live
 ### Common dcrup commands
 
 ```sh
-dcrup install stable              # latest stable prebuilt
+dcrup install stable              # latest stable prebuilt (auto: cf → gh → sf → ya)
 dcrup install 0.8.2               # pin → 0.8.2@stable
 dcrup install 0.8.2@dev
 dcrup install stable --libc musl  # Linux: musl asset (default: gnu)
+dcrup install stable --mirror cf  # CloudFlare CDN
+dcrup install stable --mirror ya  # Yandex CDN (RU fallback)
 dcrup install stable --build      # cargo build --features archive
 dcrup install night               # always build from branch dev HEAD
 dcrup default 0.8.2
@@ -60,6 +62,22 @@ dcrup which
 
 Layout: `~/.dcr/toolchains/<id>/dcr` and `~/.dcr/bin/dcr` → active version.
 
+### Download mirrors
+
+Prebuilt installs try **cf → gh → sf → ya** unless you pin a host.
+
+| Code | URL | Notes |
+|------|-----|--------|
+| `cf` | `https://cdn-global.dcr-tool.ru/<tag>/<asset>` | CloudFlare CDN (worldwide) |
+| `gh` | `https://github.com/dexoron/dcr/releases/download/<tag>/<asset>` | GitHub Releases |
+| `sf` | `https://sourceforge.net/projects/dcr-tool/files/<tag>/<asset>/download` | SourceForge |
+| `ya` | `https://cdn-ru.dcr-tool.ru/<tag>/<asset>` | Yandex CDN (RU fallback) |
+
+```sh
+dcrup install stable --mirror auto   # default
+export DCRUP_MIRROR=cf               # persist for this shell
+```
+
 ---
 
 ## Arch Linux (AUR)

docs/reference/environment-variables.mdx

@@ -57,3 +57,27 @@ export DCR_INDEX_PATH=/custom/path/index.json
 ```
 
 Default: `~/.dcr/index.json`.
+
+## DCRUP_MIRROR
+
+Download mirror for `dcrup` (prebuilt binaries only).
+
+```bash
+export DCRUP_MIRROR=auto   # cf → gh → sf → ya (default)
+export DCRUP_MIRROR=cf     # CloudFlare CDN
+export DCRUP_MIRROR=gh     # GitHub Releases
+export DCRUP_MIRROR=sf     # SourceForge
+export DCRUP_MIRROR=ya     # Yandex CDN (RU fallback)
+```
+
+CLI override: `dcrup install stable --mirror cf`.
+
+## DCRUP_HOME / DCRUP_BIN / DCRUP_REPO
+
+Installer layout and source clone URL:
+
+```bash
+export DCRUP_HOME=~/.dcr
+export DCRUP_BIN=~/.dcr/bin
+export DCRUP_REPO=https://github.com/dexoron/dcr
+```