render-askama: depend on askama_axum, or feature unification breaks consumers

crates/ogar-render-askama/Cargo.toml

@@ -9,6 +9,27 @@ description = "Build-time askama codegen harness over the canonical layer — on
 ogar-vocab = { path = "../ogar-vocab" }
 lance-graph-contract = { git = "https://github.com/AdaWorldAPI/lance-graph", branch = "main" }
 askama = "0.12"
+# `askama_axum` is NOT used by this crate — it is required to COMPILE it in any
+# graph where some other crate uses it, and that is a cargo feature-unification
+# fact, not a choice here.
+#
+# `askama_axum 0.4` enables `askama/with-axum`. Features unify across the whole
+# dependency graph, so once any consumer pulls `askama_axum`, askama's
+# `#[derive(Template)]` starts emitting an `IntoResponse` impl that names
+# `::askama_axum` — in EVERY crate that derives Template, including this one.
+# Without the dependency the expansion cannot resolve and the build dies with
+# `E0433: cannot find `askama_axum` in the crate root`, pointing at our own
+# `#[derive(Template)]` lines (measured on `artifact_kinds/cells.rs`).
+#
+# The defect is therefore invisible until a consumer combines the two, and then
+# it is unfixable from the consumer side without forking or pinning this crate.
+# Measured 2026-08-20 wiring `ogar-render-askama` into `medcare-server`, which
+# has used `askama_axum = "0.4"` for its own handlers all along.
+#
+# Cheap and inert where nobody enables the feature: `askama_axum` is a thin
+# adapter over the same askama, and with the feature off the derive never
+# references it.
+askama_axum = "0.4"
 
 [dev-dependencies]
 # harvest driver for examples/render_osm.rs (Rails app/models → Class → Rust)

crates/ogar-render-askama/tests/axum_feature_unification.rs

@@ -0,0 +1,48 @@
+//! **The `askama_axum` dependency is load-bearing and must not be tidied away.**
+//!
+//! This crate never calls `askama_axum`. A dependency-hygiene pass (`cargo
+//! machete`, a "remove unused deps" cleanup, a reviewer asking "why is this
+//! here?") will therefore read it as dead weight and delete it — and the
+//! deletion is invisible, because every test in this repository still passes.
+//!
+//! It breaks CONSUMERS instead, and only those that combine two innocuous
+//! choices:
+//!
+//! ```text
+//! consumer  ──> askama_axum 0.4        (its own axum handlers)
+//!           └─> ogar-render-askama     (this crate)
+//!
+//! askama_axum 0.4 enables askama/with-axum
+//!           ↓  (cargo unifies features across the WHOLE graph)
+//! askama's #[derive(Template)] now emits `impl IntoResponse` naming
+//! `::askama_axum` — in every crate that derives Template, including this one
+//!           ↓
+//! error[E0433]: cannot find `askama_axum` in the crate root
+//!   --> crates/ogar-render-askama/src/artifact_kinds/cells.rs:21
+//! ```
+//!
+//! Measured 2026-08-20 wiring this crate into `AdaWorldAPI/MedCare-rs`'s
+//! `medcare-server`, which has used `askama_axum = "0.4"` for its own handlers
+//! all along. The consumer cannot fix it: the failure is inside THIS crate's
+//! derives, so the only consumer-side escapes are forking or pinning, and the
+//! workspace doctrine forbids both.
+//!
+//! # What this test can and cannot prove
+//!
+//! It CANNOT reproduce the failure: the trigger is a feature enabled by a
+//! sibling package, and a test in this crate cannot enable it on the consumer's
+//! behalf. Honest limitation, stated rather than dressed up.
+//!
+//! What it DOES do is make the dependency reachable from source, so removing it
+//! fails to compile here instead of failing in a downstream repository weeks
+//! later. That is the whole job.
+
+/// Referenced so the dependency is used from source. Deleting the
+/// `askama_axum` dependency breaks this line — which is the point.
+#[test]
+fn the_askama_axum_dependency_is_referenced_so_it_cannot_be_tidied_away() {
+    use askama_axum as _;
+    // The version that carries the `with-axum` feature this crate's derives
+    // start depending on the moment any consumer enables it.
+    assert!(!env!("CARGO_PKG_NAME").is_empty());
+}