feat(install): support SENTRY_VERSION env var for version pinning

Add SENTRY_VERSION environment variable to the curl install script so
users can pin a version without inline flags. Useful for CI/CD pipelines
and Dockerfiles. The --version flag takes precedence if both are set.

- Read SENTRY_VERSION as the default for requested_version in install script
- Add SENTRY_VERSION to the usage help text and examples
- Document in getting-started.mdx with stable and nightly examples
- Add to configuration.md environment variables reference

Author: BYK

docs/src/content/docs/configuration.md

@@ -71,6 +71,16 @@ Override the directory where the CLI stores its database (credentials, caches, d
 export SENTRY_CONFIG_DIR=/path/to/config
 ```
 
+### `SENTRY_VERSION`
+
+Pin a specific version for the [install script](./getting-started/#install-script). Accepts a version number (e.g., `0.19.0`) or `nightly`. The `--version` flag takes precedence if both are set.
+
+```bash
+SENTRY_VERSION=nightly curl https://cli.sentry.dev/install -fsS | bash
+```
+
+This is useful in CI/CD pipelines and Dockerfiles where you want reproducible installations without inline flags.
+
 ### `SENTRY_PLAIN_OUTPUT`
 
 Force plain text output (no colors or ANSI formatting). Takes precedence over `NO_COLOR`.

docs/src/content/docs/getting-started.mdx

@@ -21,6 +21,18 @@ Install the nightly build (built from `main`, updated on every commit):
 curl https://cli.sentry.dev/install -fsS | bash -s -- --version nightly
 ```
 
+You can also use the `SENTRY_VERSION` environment variable to pin a version,
+which is especially useful in CI/CD pipelines and Dockerfiles:
+
+```bash
+# Pin to a specific stable version
+SENTRY_VERSION=0.19.0 curl https://cli.sentry.dev/install -fsS | bash
+
+# Pin to nightly
+SENTRY_VERSION=nightly curl https://cli.sentry.dev/install -fsS | bash
+```
+
+The `--version` flag takes precedence over `SENTRY_VERSION` if both are set.
 The chosen channel is persisted so that `sentry cli upgrade` automatically
 tracks the same channel on future updates.
 

install

@@ -88,16 +88,18 @@ Options:
 
 Environment Variables:
     SENTRY_INSTALL_DIR      Override the installation directory
+    SENTRY_VERSION          Install a specific version (e.g., 0.19.0, nightly)
 
 Examples:
     curl -fsSL https://cli.sentry.dev/install | bash
     curl -fsSL https://cli.sentry.dev/install | bash -s -- --version nightly
-    curl -fsSL https://cli.sentry.dev/install | bash -s -- --version 0.2.0
+    curl -fsSL https://cli.sentry.dev/install | bash -s -- --version 0.19.0
+    SENTRY_VERSION=nightly curl -fsSL https://cli.sentry.dev/install | bash
     SENTRY_INSTALL_DIR=~/.local/bin curl -fsSL https://cli.sentry.dev/install | bash
 EOF
 }
 
-requested_version=""
+requested_version="${SENTRY_VERSION:-}"
 no_modify_path=false
 no_completions=false
 while [[ $# -gt 0 ]]; do