Automate boot unit inclusion with architecture-aware Moderne analysis

- Replace boot.mgr's static unit list with generated dangling_units.inc
- Generate Pascal LSTs and run the dangling-unit recipe before compilation
- Exclude Wasuro, inactive architectures, and NOT_DANGLING units
- Add ASURO_ARCH selection with an x86 default
- Mark unfinished legacy units as NOT_DANGLING
- Inherit pinned Moderne tooling in the builder image
- Ensure Drone pulls the latest builder image
- Document the updated build pipeline in MkDocs

Validation:
- Full x86 ISO build and VirtualBox boot succeeded
- 1,133 kernel tests passed with no failures
- x86_64 build failed clearly due to unavailable sources

toolchain/compile_sources.sh

@@ -1,13 +1,21 @@
 #!/usr/bin/env bash
+set -euo pipefail
+source "$(dirname "${BASH_SOURCE[0]}")/architecture.sh"
 echo " "
 echo "======================="
 echo " "
 echo "Compiling FPC Sources..."
 echo " "
-# Build -Fu flags for all directories under src/, wasuro/ and compat/
-FU_PATHS="-Fusrc -Fuwasuro -Fucompat"
-for dir in $(find src wasuro compat -type d 2>/dev/null); do
-    FU_PATHS="$FU_PATHS -Fu$dir"
-done
+# Keep other architectures out of FPC's unit resolution, including arch/ itself.
+FU_PATHS=()
+while IFS= read -r -d '' dir; do
+    FU_PATHS+=("-Fu$dir")
+done < <(find src wasuro compat -path src/arch -prune -o -type d -print0
+         find "src/arch/$ASURO_ARCH" -type d -print0)
 
-fpc -Aelf -gw -g -gl -n -v0e -O3 -OpPENTIUM3 -Si -Sc -Sg -Xd -CX -XXs -CfSSE -CfSSE2 -Rintel -Pi386 -Tlinux -FElib/ $FU_PATHS src/asuro.pas
+if [[ "$ASURO_ARCH" == "x86" ]]; then
+    fpc -Aelf -gw -g -gl -n -v0e -O3 -OpPENTIUM3 -Si -Sc -Sg -Xd -CX -XXs -CfSSE -CfSSE2 -Rintel -Pi386 -Tlinux -FElib/ "${FU_PATHS[@]}" src/asuro.pas
+else
+    echo "No compiler found for target: $ASURO_ARCH" >&2
+    exit 1
+fi