docs(cache): correct the furyrs invocation count — five compiling, four feature sets

plans/cargo-dependency-cache.md

@@ -30,7 +30,7 @@ Entry #12 proposed the `cargo-chef` principle: pre-build a dependency-only
 
 **1. The build command is opaque to us.** The orchestrator receives
 `build-command` as a single string and runs it. furyrs's pipeline is five
-distinct cargo invocations with three different feature sets. `cargo chef cook`
+compiling cargo invocations across four feature configurations. `cargo chef cook`
 must be handed the same flags as the real build to produce the right dependency
 graph — we do not have them, and parsing an arbitrary shell string to recover
 them is a guess that fails silently (a wrong cook produces a cache that misses
@@ -1290,8 +1290,10 @@ At the time of writing that block runs, in order: `cargo fmt --all -- --check`,
 ddr5-scaffold --locked`, `cargo clippy -p fury-cli --all-targets --features
 direct-backend --locked -- -D warnings`, `cargo clippy --workspace
 --all-targets --locked -- -D warnings`, `cargo clippy -p fury-gui --features
-gui --bin fury-gui --locked -- -D warnings`, and `cargo audit`. Three distinct
-feature sets, which is exactly the case the single-entry design has to handle.
+gui --bin fury-gui --locked -- -D warnings`, and `cargo audit`. Five of those
+compile, across four feature configurations — default, `ddr5-scaffold`,
+`direct-backend`, `gui` — which is exactly the case the single-entry design has
+to handle.
 
 Expected in the log: `[cache] miss for v1-… — building cold`, then
 `[cache] prune: ok — N workspace member(s) stripped`, then