nix: comments state current behaviour, not history

Rewrite comments and option descriptions under nix/ that narrate how the
code got here ("used to", "new name", "sat at the TOP", "no longer",
renamed/moved narration, attributions) to say what the code does now and
why. Comments and description strings only; no logic changes.

Files in open PR #4970's diff are left alone. Refs #3902

nix/packages/default.nix

@@ -61,10 +61,10 @@ let
   # derivation means a prompt edit doesn't bust the cargo cache.
   #
   # …and the dep cache underneath is the one WITHOUT test targets. This
-  # derivation has never run a test — `doCheck = false` below says so —
-  # but it used to sit on a cache that compiled every dev-dependency and
-  # test harness anyway, work whose only consumers are the checks. A
-  # deploy paid for it on every toolchain or dependency change.
+  # derivation never runs a test — `doCheck = false` below says so — so it
+  # sits on a cache that skips every dev-dependency and test harness, work
+  # whose only consumers are the checks. Compiling them here would make a
+  # deploy pay for it on every toolchain or dependency change.
   workspaceBuild = craneLib.buildPackage {
     src = cleanSrc;
     cargoArtifacts = cargoArtifactsBinOnly;

nix/packages/frontend.nix

@@ -38,9 +38,9 @@ buildNpmPackage {
   # Read from `../../frontend/npm-deps-hash`, the single source of
   # truth `./swarm-ui.nix` and `../checks.nix`'s `swarm-ui-typecheck`
   # also read — all three build from the one `frontend/package-lock.json`,
-  # so one file keeps them from drifting independently (this used to be
-  # a hardcoded copy per derivation, and only some of the three got
-  # updated the one time the lockfile changed). Regenerate with
+  # so one file keeps them from drifting independently (a hardcoded copy
+  # per derivation would let some of the three miss a lockfile change).
+  # Regenerate with
   # `prefetch-npm-deps frontend/package-lock.json` and overwrite the
   # file whenever the lockfile changes.
   npmDepsHash = builtins.readFile ../../frontend/npm-deps-hash;

nix/packages/swagger-ui-dist.nix

@@ -5,10 +5,10 @@
 
 # Pure vendored Swagger UI 5.17.14 static dist — no hyperhive theming
 # (see ./swagger-ui-theme.nix for that layer). Deliberately NOT sourced
-# via the Rust `utoipa-swagger-ui-vendored` crate / Cargo.lock (per the
-# operator's ask: a nix package that just contains the plain static
-# dist, not fetched via cargo) — hive-c0re no longer needs to know this
-# exists at all once the gateway hosts it directly.
+# via the Rust `utoipa-swagger-ui-vendored` crate / Cargo.lock: this is a
+# nix package that just contains the plain static dist, not fetched via
+# cargo — hive-c0re does not need to know this exists, because the
+# gateway hosts it directly.
 #
 # Sourced straight from the `swagger-ui-dist` npm package, which ships
 # exactly the built `dist/` files (no source, no build step needed) at

nix/packages/swagger-ui-theme.nix

@@ -21,7 +21,7 @@
 #                           `{{config}}` placeholder its OWN build.rs
 #                           injects (`replace_default_url_with_config`
 #                           + `format_config`); hive-c0re doesn't serve
-#                           this file at all anymore, so that rewrite
+#                           this file at all, so that rewrite
 #                           is baked in statically here instead —
 #                           hand-verified byte-for-byte against what
 #                           `format_config` would produce, by applying