decouple abstraction phase1:1

phase1 step1: introduce sisudoc.abstraction package re-export surface

Create src/sisudoc/abstraction/package.d as a library-facing re-export
module for the document-abstraction stage.

The surface currently re-exports:
- sisudoc.meta.metadoc          (spineAbstraction, A-layer entry)
- sisudoc.meta.metadoc_from_src (docAbstraction, B-layer entry)

No code moves; no behaviour change. The package exists so external
consumers can `import sisudoc.abstraction;` and reach the entry points
without depending on spine's internal directory layout.

(assisted by Claude-Code)

1 files changed, 44 insertions, 0 deletions

diff --git a/org/ocda.org b/org/ocda.org
index 31d4c79..aab5f2a 100644
--- a/org/ocda.org
+++ b/org/ocda.org
@@ -22,6 +22,50 @@
 
 - Process markup document, create document abstraction
 
+** library template :module:metadoc_from_src:
+
+#+HEADER: :tangle "../src/sisudoc/abstraction/package.d"
+#+HEADER: :noweb yes
+#+BEGIN_SRC d
+<<doc_header_including_copyright_and_license>>
+/++
+  sisudoc.abstraction - public surface of the document-abstraction
+  library.
+
+  Pipeline position: markup -> abstraction -> output.
+  This package is the abstraction stage. The output stage lives in
+  sisudoc.io_out and consumes the values produced here.
+
+  Entry points:
+    - spineAbstraction!() (from sisudoc.meta.metadoc) - A-layer:
+        builds the in-memory document object model from a manifest
+        (pod path, .sst path). Reads the document body, parses YAML
+        headers, returns a struct with .abstraction (the object
+        model) and .matters (the conf/meta/src wrapper).
+    - docAbstraction!()   (from sisudoc.meta.metadoc_from_src) -
+        B-layer: builds the abstraction from already-loaded body
+        text plus a pre-built ConfComposite. Pure, no file I/O.
+
+  The A-layer is a thin wrapper over the B-layer; consumers that
+  want a minimal-dependency entry should use docAbstraction!()
+  directly.
+
+  Serialisation:
+    - sisudoc.abstraction.ssp - PEG-parsable text serialisation of
+        the abstraction (the .ssp format). See specs/doc-abstraction-
+        format/ for the format reference.
+
+  This file is a re-export-only surface. No logic lives here; it
+  exists so external consumers can `import sisudoc.abstraction;` and
+  reach the entry points without depending on spine's directory
+  layout.
++/
+module sisudoc.abstraction;
+@safe:
+public import sisudoc.meta.metadoc;          // spineAbstraction (A-layer)
+public import sisudoc.meta.metadoc_from_src; // docAbstraction   (B-layer)
+#+END_SRC
+
 ** _module template_ :module:metadoc_from_src:
 
 #+HEADER: :tangle "../src/sisudoc/meta/metadoc_from_src.d"