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

doc/toolchain/dangling_units.md

@@ -0,0 +1,45 @@
+# Automatic boot-unit inclusion
+
+Run the usual `docker compose build builder` and `docker compose run builder`
+from Asuro. Only this repository is required. Compose and Drone use the same
+Dockerfile and repository build context, producing `t3hn3rd/asuro-build:latest`.
+The Dockerfile inherits the published `t3hn3rd/moderne-asuro-recipes:0.1.1` image,
+pinned by digest. It already includes Java, Moderne CLI, the Pascal LST generator,
+and the registered recipe. The Asuro layer installs FPC and the kernel build tools.
+
+To upgrade tooling, publish the upstream images first and update `RECIPES_IMAGE`
+in the Dockerfile to the new tag and digest. Local tooling image testing can use
+`docker compose build --build-arg RECIPES_IMAGE=<local-tag> builder`.
+
+`ASURO_ARCH` selects the source architecture, defaulting to `x86`. For example:
+
+```sh
+export ASURO_ARCH=x86
+docker compose run --rm builder
+```
+
+Compose forwards this variable to the builder; Drone inherits it from its compile
+environment. Only `src/arch/$ASURO_ARCH` is added to FPC's unit search paths.
+Other architecture folders are excluded from LST generation and from the recipe's
+dependency graph and results. Common units outside `src/arch` remain eligible.
+The selected architecture folder must exist. This source selection does not
+change the existing i386 compiler target, assembly stub, or linker settings;
+an x86_64 port still needs those platform-specific changes.
+
+`compile_dangling.sh` runs after Wasuro synchronization and before FPC. It copies
+only `src/` and `compat/` into an isolated temporary analysis repository, generates
+LSTs with rewrite-pascal, runs the standalone Moderne recipe, exports its
+datatable, and writes `src/boot/dangling_units.inc`. Wasuro is not parsed.
+Datatable conversion is provided by the standalone project's Java exporter.
+Parse errors, recipe failures, and malformed datatables stop the build. The
+generated include is ignored by Git and removed before each generation attempt.
+
+Use `{$DEFINE NOT_DANGLING}` near a unit declaration to exclude an experimental
+or legacy unit from automatic inclusion. It can still be referenced normally.
+This is a file-level marker; conditional definitions are not evaluated. The
+analysis follows both interface and implementation uses, without expanding
+includes or evaluating conditional compilation.
+
+Moderne runs through its CLI normally; any license or tenant configuration
+required by your CLI installation must be provided to the container separately.
+No host credentials are copied into the image.