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/host-modules/hive-ci.nix

@@ -207,11 +207,8 @@ in
 
     # `caTrust.containerOrdering` orders this unit after `hive-tls-ca.service`
     # in self-signed mode (see the hive-ca-trust helper). Runner registration
-    # is no longer on the boot-critical path — hive-c0re owns it out of band —
-    # so the container boots immediately and needs no start-timeout bump. The
-    # former `TimeoutStartSec = mkForce "180s"` band-aid (which papered over a
-    # boot-path forge + core-token round-trip that could trip the nspawn start
-    # timeout into a ~60s restart loop) is gone with that move.
+    # is not on the boot-critical path — hive-c0re owns it out of band — so
+    # the container boots immediately and needs no start-timeout bump.
     systemd.services."container@hive-ci" = caTrust.containerOrdering;
 
     containers.hive-ci = {
@@ -415,7 +412,7 @@ in
             # runner stays down (Restart=on-failure retries) until c0re
             # registers it, rather than blocking the container's start.
             #
-            # No nix-daemon wait anymore: builds route through the HOST daemon
+            # No nix-daemon wait: builds route through the HOST daemon
             # (bound socket above), which is up before the container — nix's
             # own connect retries cover any brief window. `mkBefore` runs this
             # ahead of any upstream pre-steps.