docs: Remove empty developer guide pages (#9026)

- Remove empty "embedding Vortex" pages from docs.
- Remove `make.bat`
- Move C++ quickstart to quickstart folder.
- Update duckdb docs for newer read syntax.
- Remove obsolete duckdb developer quide page.

---------

Signed-off-by: Mikhail Kot <mikhail@spiraldb.com>
Signed-off-by: myrrc <mikhail@spiraldb.com>

Author: myrrc

docs/api/index.md

@@ -11,6 +11,5 @@ maxdepth: 2
 python/index
 Rust API <https://docs.rs/vortex>
 c/index
-cpp/index
 java/index
 ```

docs/developer-guide/embedding/cxx.md

@@ -8,7 +8,6 @@ maxdepth: 2
 ---
 
 extending/index
-embedding/index
 language-bindings
 benchmarking
 ```
@@ -37,6 +36,5 @@ caption: Integrations
 ---
 
 integrations/datafusion
-integrations/duckdb
 integrations/spark
 ```

docs/developer-guide/embedding/ffi.md

@@ -1,10 +1,9 @@
-C++ API
-=======
+C++ Quickstart
+==============
 
-The Vortex C++ API allows you to read and write ``.vortex`` files directly or
-via an Arrow compatibility layer like `nanoarrow
-<https://arrow.apache.org/nanoarrow/>`_. The only dependency apart from Vortex
-is ``nanoarrow``.
+Vortex C++ API allows you to read and write ``.vortex`` files directly or via
+an Arrow compatibility layer like `nanoarrow <https://arrow.apache.org/nanoarrow/>`_.
+The only dependency apart from Vortex is ``nanoarrow``.
 
 .. note::
    C++ API is a work in progress. Please reach out to us if you are interested
@@ -57,7 +56,7 @@ Assuming you have Vortex files ``people0``, ``people1``, and ``me`` in a local f
 each containing U8 column "age" and U16 column "height", this is how you
 print all ages for specific heights:
 
-.. literalinclude:: ../../../lang/cpp/examples/reader.cpp
+.. literalinclude:: ../../lang/cpp/examples/reader.cpp
    :language: cpp
    :start-after: docs:begin:example
    :end-before: docs:end:example
@@ -148,7 +147,7 @@ Now let's write the first files to be read by our previous example.
 Source code for this example is `writer.cpp
 <https://github.com/vortex-data/vortex/tree/develop/lang/cpp/examples/writer.cpp>`_.
 
-.. literalinclude:: ../../../lang/cpp/examples/writer.cpp
+.. literalinclude:: ../../lang/cpp/examples/writer.cpp
    :language: cpp
    :start-after: docs:begin:example
    :end-before: docs:end:example

docs/developer-guide/embedding/gpu.md

@@ -24,5 +24,6 @@ caption: Language Libraries
 
 Python Quickstart <python>
 Rust Quickstart <rust>
+C++ Quickstart <cpp>
 Java Quickstart <java>
 ```