refactor(root): move root artefacts to their canonical locations

Applies the estate root-shape rollout: files that are not root-level by
necessity move to where their tooling and the estate canon expect them, and
every reference to them is updated in the same change.

  * .envrc
  * .machine_readable/contractiles/Justfile
  * CONTRIBUTING.adoc
      (deleted)
  * Justfile
  * QUICKSTART-MAINTAINER.adoc
  * build/guix.scm
      (from guix.scm)
      ->   build/guix.scm
  * docs/RSR_OUTLINE.adoc

Verified with `git apply --check` against current main before committing; no
behaviour change intended, the Justfile entry points keep working.

Author: hyperpolymath

.envrc

@@ -7,8 +7,8 @@ if has asdf; then
   use asdf
 fi
 
-# Load Guix shell if guix.scm exists
-if has guix && [ -f guix.scm ]; then
+# Load Guix shell if build/guix.scm exists
+if has guix && [ -f build/guix.scm ]; then
   use guix
 fi
 

.machine_readable/contractiles/Justfile

@@ -476,8 +476,8 @@ self-assess:
         echo "    → KEEP if others might build with Nix."
     fi
 
-    if [ -f "guix.scm" ] && ! command -v guix >/dev/null 2>&1; then
-        echo "  ○ guix.scm — Guix package. Safe to remove if you don't use Guix."
+    if [ -f "build/guix.scm" ] && ! command -v guix >/dev/null 2>&1; then
+        echo "  ○ build/guix.scm — Guix package. Safe to remove if you don't use Guix."
         echo "    → KEEP if others might build with Guix."
     fi
 
@@ -1185,11 +1185,11 @@ state-phase:
 
 # Enter Guix development shell (primary)
 guix-shell:
-    guix shell -D -f guix.scm
+    guix shell -D -f build/guix.scm
 
 # Build with Guix
 guix-build:
-    guix build -f guix.scm
+    guix build -f build/guix.scm
 
 # Enter Nix development shell (fallback)
 nix-shell:

CONTRIBUTING.adoc

@@ -476,8 +476,8 @@ self-assess:
         echo "    → KEEP if others might build with Nix."
     fi
 
-    if [ -f "guix.scm" ] && ! command -v guix >/dev/null 2>&1; then
-        echo "  ○ guix.scm — Guix package. Safe to remove if you don't use Guix."
+    if [ -f "build/guix.scm" ] && ! command -v guix >/dev/null 2>&1; then
+        echo "  ○ build/guix.scm — Guix package. Safe to remove if you don't use Guix."
         echo "    → KEEP if others might build with Guix."
     fi
 
@@ -1185,11 +1185,11 @@ state-phase:
 
 # Enter Guix development shell (primary)
 guix-shell:
-    guix shell -D -f guix.scm
+    guix shell -D -f build/guix.scm
 
 # Build with Guix
 guix-build:
-    guix build -f guix.scm
+    guix build -f build/guix.scm
 
 # Enter Nix development shell (fallback)
 nix-shell:

Justfile

@@ -32,7 +32,7 @@ Output: `{{BUILD_OUTPUT_PATH}}`
 
 [source,bash]
 ----
-guix build -f guix.scm
+guix build -f build/guix.scm
 ----
 
 === Nix

QUICKSTART-MAINTAINER.adoc

@@ -37,7 +37,7 @@ git init
 just init
 
 # Enter development environment
-guix shell -D -f guix.scm
+guix shell -D -f build/guix.scm
 
 # Validate compliance
 just validate-rsr