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, 85 insertions, 0 deletions

diff --git a/src/sisudoc/abstraction/package.d b/src/sisudoc/abstraction/package.d
new file mode 100644
index 0000000..74110f6
--- /dev/null
+++ b/src/sisudoc/abstraction/package.d
@@ -0,0 +1,85 @@
+/+
+- Name: SisuDoc Spine, Doc Reform [a part of]
+  - Description: documents, structuring, processing, publishing, search
+    - static content generator
+
+  - Author: Ralph Amissah
+    [ralph.amissah@gmail.com]
+
+  - Copyright: (C) 2015 (continuously updated, current 2026) Ralph Amissah, All Rights Reserved.
+
+  - License: AGPL 3 or later:
+
+    Spine (SiSU), a framework for document structuring, publishing and
+    search
+
+    Copyright (C) Ralph Amissah
+
+    This program is free software: you can redistribute it and/or modify it
+    under the terms of the GNU AFERO General Public License as published by the
+    Free Software Foundation, either version 3 of the License, or (at your
+    option) any later version.
+
+    This program is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+    more details.
+
+    You should have received a copy of the GNU General Public License along with
+    this program. If not, see [https://www.gnu.org/licenses/].
+
+    If you have Internet connection, the latest version of the AGPL should be
+    available at these locations:
+    [https://www.fsf.org/licensing/licenses/agpl.html]
+    [https://www.gnu.org/licenses/agpl.html]
+
+  - Spine (by Doc Reform, related to SiSU) uses standard:
+    - docReform markup syntax
+      - standard SiSU markup syntax with modified headers and minor modifications
+    - docReform object numbering
+      - standard SiSU object citation numbering & system
+
+  - Homepages:
+    [https://www.sisudoc.org]
+    [https://www.doc-reform.org]
+
+  - Git
+    [https://git.sisudoc.org/]
+
++/
+/++
+  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)