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_dangling.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+echo "Generating dangling Pascal units..."
+TOOLCHAIN_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+cd "${TOOLCHAIN_DIR}/.."
+source "$TOOLCHAIN_DIR/architecture.sh"
+OUT="$(pwd)/src/boot/dangling_units.inc"
+# Remove stale output before attempting analysis. Work in a separate temporary
+# repository so developer Moderne runs and generated sources cannot contaminate it.
+rm -f "$OUT"
+WORK="$(mktemp -d)"
+trap 'rm -rf "$WORK"' EXIT
+mkdir -p "$WORK/src" "$WORK/compat"
+cp -a src/. "$WORK/src/"
+cp -a compat/. "$WORK/compat/"
+# Do not parse inactive architectures: incomplete ports must not break this build.
+for dir in "$WORK/src/arch/"*; do
+    [[ "$(basename "$dir")" == "$ASURO_ARCH" ]] || rm -rf "$dir"
+done
+git -C "$WORK" init -q
+git -C "$WORK" remote add origin https://gitea.spexeah.com/Spexeah/Asuro.git
+PASCAL_JAVA_OPTIONS='-Dpascal.sourceRoots=src,compat -Dpascal.failOnParseError=true' pascal-lst "$WORK"
+mod run "$WORK" --recipe org.openrewrite.pascal.boot.FindDanglingUnits \
+    --recipe-option "architecture=$ASURO_ARCH"
+dangling-include "$WORK" "$OUT"