docs: drop dangling stapeln references after manifest removal

Follow-on to the stapeln.toml deletion: remove the now-broken
'Container (Stapeln)' quickstart options and the stapeln.toml mention in
EXPLAINME (these pointed at the deleted build manifest / non-existent
just recipes).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016t5KLJDtqdeDi1EMNqNx6K

Author: claude

EXPLAINME.adoc

@@ -221,7 +221,7 @@ progress across all languages from this coordinator
 | Every RSR repo in the account
 
 | *Stapeln containers*
-| `stapeln.toml` — compiler toolchain containers
+| Account-wide layered container tool; the coordinator ships no build container (it contains no language code to build)
 | All containerised services in the account
 |===
 

QUICKSTART-MAINTAINER.adoc

@@ -42,14 +42,6 @@ guix build -f guix.scm
 nix build
 ----
 
-=== Container (Stapeln)
-
-[source,bash]
-----
-just stapeln-export    # Generates Containerfile
-podman build -t nextgen-languages .
-----
-
 === Manual Package
 
 [source,bash]

QUICKSTART-USER.adoc

@@ -51,14 +51,7 @@ The setup script will:
 * Offer install location choices
 * Run a self-diagnostic to verify everything works
 
-=== Option 2: Container (via Stapeln)
-
-[source,bash]
-----
-just stapeln-run
-----
-
-=== Option 3: Portable (no system changes)
+=== Option 2: Portable (no system changes)
 
 [source,bash]
 ----