Missing added_in on new env vars (#16217)

## Summary

Adds the version for environment variables added in
https://github.com/astral-sh/uv/pull/16040 and
https://github.com/astral-sh/uv/pull/16125. as these were in-flight
before documentation versioning was added.

Adds ability to emit a compiler error when added in is missing for
improved reporting to the developer.

e.g. example for the ones fixed in this PR

```shell
error: missing #[attr_added_in("x.y.z")] on `UV_UPLOAD_HTTP_TIMEOUT`
       note: env vars for an upcoming release should be annotated with `#[attr_added_in("next release")]`
   --> crates\uv-static\src\env_vars.rs:593:15
    |
593 |     pub const UV_UPLOAD_HTTP_TIMEOUT: &'static str = "UV_UPLOAD_HTTP_TIMEOUT";
    |               ^^^^^^^^^^^^^^^^^^^^^^

error: missing #[attr_added_in("x.y.z")] on `UV_WORKING_DIRECTORY`
       note: env vars for an upcoming release should be annotated with `#[attr_added_in("next release")]`
    --> crates\uv-static\src\env_vars.rs:1087:15
     |
1087 |     pub const UV_WORKING_DIRECTORY: &'static str = "UV_WORKING_DIRECTORY";
     |               ^^^^^^^^^^^^^^^^^^^^
error: could not compile `uv-static` (lib) due to 2 previous errors
```

crates/uv-macros/src/lib.rs

@@ -1,7 +1,8 @@
 mod options_metadata;
 
 use proc_macro::TokenStream;
-use quote::quote;
+use quote::{quote, quote_spanned};
+use syn::spanned::Spanned;
 use syn::{Attribute, DeriveInput, ImplItem, ItemImpl, LitStr, parse_macro_input};
 
 #[proc_macro_derive(OptionsMetadata, attributes(option, doc, option_group))]
@@ -109,14 +110,14 @@ pub fn attribute_env_vars_metadata(_attr: TokenStream, input: TokenStream) -> To
                     return None;
                 };
                 let name = lit.value();
-                Some((name, doc, added_in))
+                Some((name, doc, added_in, item.ident.span()))
             }
             ImplItem::Fn(item) if !is_hidden(&item.attrs) => {
                 // Extract the environment variable patterns.
                 if let Some(pattern) = get_env_var_pattern_from_attr(&item.attrs) {
                     let doc = get_doc_comment(&item.attrs);
                     let added_in = get_added_in(&item.attrs);
-                    Some((pattern, doc, added_in))
+                    Some((pattern, doc, added_in, item.sig.span()))
                 } else {
                     None // Skip if pattern extraction fails.
                 }
@@ -125,8 +126,25 @@ pub fn attribute_env_vars_metadata(_attr: TokenStream, input: TokenStream) -> To
         })
         .collect();
 
+    // Look for missing attr_added_in and issue a compiler error if any are found.
+    let added_in_errors: Vec<_> = constants
+        .iter()
+        .filter_map(|(name, _, added_in, span)| {
+            added_in.is_none().then_some({
+                let msg = format!(
+                    "missing #[attr_added_in(\"x.y.z\")] on `{name}`\nnote: env vars for an upcoming release should be annotated with `#[attr_added_in(\"next release\")]`"
+                );
+                quote_spanned! {*span => compile_error!(#msg); }
+            })
+        })
+        .collect();
+
+    if !added_in_errors.is_empty() {
+        return quote! { #ast #(#added_in_errors)* }.into();
+    }
+
     let struct_name = &ast.self_ty;
-    let pairs = constants.iter().map(|(name, doc, added_in)| {
+    let pairs = constants.iter().map(|(name, doc, added_in, _span)| {
         if let Some(added_in) = added_in {
             quote! { (#name, #doc, Some(#added_in)) }
         } else {

crates/uv-static/src/env_vars.rs

@@ -1,6 +1,5 @@
 //! Environment variables used or supported by uv.
 //! Used to generate `docs/reference/environment.md`.
-//! NOTICE: Upcoming release functionality should be documented with `#[attr_added_in("0.9.1")]`.
 use uv_macros::{attr_added_in, attr_env_var_pattern, attr_hidden, attribute_env_vars_metadata};
 
 /// Declares all environment variable used throughout `uv` and its crates.
@@ -591,6 +590,7 @@ impl EnvVars {
     pub const NO_PROXY: &'static str = "NO_PROXY";
 
     /// Timeout (in seconds) for only upload HTTP requests. (default: 900 s)
+    #[attr_added_in("0.9.1")]
     pub const UV_UPLOAD_HTTP_TIMEOUT: &'static str = "UV_UPLOAD_HTTP_TIMEOUT";
 
     /// Timeout (in seconds) for HTTP requests. (default: 30 s)
@@ -1085,6 +1085,7 @@ impl EnvVars {
     pub const UV_PROJECT: &'static str = "UV_PROJECT";
 
     /// Equivalent to the `--directory` command-line argument.
+    #[attr_added_in("0.9.1")]
     pub const UV_WORKING_DIRECTORY: &'static str = "UV_WORKING_DIRECTORY";
 
     /// Disable GitHub-specific requests that allow uv to skip `git fetch` in some circumstances.

docs/reference/environment.md

@@ -652,6 +652,7 @@ Used ephemeral environments like CI to install uv to a specific path while preve
 the installer from modifying shell profiles or environment variables.
 
 ### `UV_UPLOAD_HTTP_TIMEOUT`
+<small class="added-in">added in `0.9.1`</small>
 
 Timeout (in seconds) for only upload HTTP requests. (default: 900 s)
 
@@ -670,6 +671,7 @@ created by `uv venv`.
 Note that `setuptools` and `wheel` are not included in Python 3.12+ environments.
 
 ### `UV_WORKING_DIRECTORY`
+<small class="added-in">added in `0.9.1`</small>
 
 Equivalent to the `--directory` command-line argument.