Phase 7.5: Doxygen infrastructure + Phase 8 design freeze

Adds the Doxygen documentation pipeline as the bridge from Phase 7
(porting complete) to Phase 8 (CGAL package). Also captures the
strategic Phase 8 decisions taken on 2026-05-19.

Infrastructure
──────────────
* Doxyfile         — CGAL-style minimal configuration, HTML-only,
                     INPUT=code/include + doc/, excludes deps/ and
                     macOS Finder duplicates
* code/CMakeLists  — `doc` target via find_package(Doxygen QUIET);
                     silently disabled if Doxygen is not installed
* README           — `cmake --build build --target doc` instructions
* .gitignore       — exclude doc/doxygen/ output

Phase 8 strategic decisions (recorded in doc/api/cgal-package.md)
────────────────────────────────────────────────────────────────
* Submission to CGAL: pre-submission-ready, 12+ months horizon, MIT preserved
* Mesh-type flexibility: generic FaceGraph + HalfedgeGraph
* Parameter style: CGAL Named Parameters
* Default kernel: Simple_cartesian<double> (status quo)
* Architecture: 3-layer wrapper, no algorithm duplication
* Acceptance test: Phase 9a (Inversive-Distance) as first new client

CLAUDE.md updated with a compact Phase 8 decision table.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Doxyfile

@@ -0,0 +1,126 @@
+# Doxyfile for conformallab++
+#
+# Phase 7.5 — minimal CGAL-style Doxygen configuration.
+# Only non-default values are set; Doxygen ≥ 1.9.5 supplies the rest.
+#
+# Usage:
+#   doxygen Doxyfile           # generates HTML into doc/doxygen/html/
+#   open doc/doxygen/html/index.html
+#
+# Or via CMake:
+#   cmake --build build --target doc
+
+# ── Project identity ─────────────────────────────────────────────────────────
+PROJECT_NAME           = "conformallab++"
+PROJECT_NUMBER         = 0.7.0
+PROJECT_BRIEF          = "Discrete conformal maps on triangle meshes — C++17 reimplementation of ConformalLab (TU Berlin)"
+PROJECT_LOGO           =
+OUTPUT_DIRECTORY       = doc/doxygen
+USE_MDFILE_AS_MAINPAGE = README.md
+
+# ── Input ────────────────────────────────────────────────────────────────────
+INPUT                  = README.md \
+                         CLAUDE.md \
+                         code/include \
+                         doc/api \
+                         doc/architecture \
+                         doc/math
+FILE_PATTERNS          = *.hpp *.h *.cpp *.md
+RECURSIVE              = YES
+EXCLUDE_PATTERNS       = */build*/* \
+                         */deps/* \
+                         */.git/* \
+                         */test-reports/* \
+                         */* 2.hpp
+EXCLUDE_SYMBOLS        = Eigen::* boost::* std::*
+
+# ── Source browsing ──────────────────────────────────────────────────────────
+EXTRACT_ALL            = YES
+EXTRACT_PRIVATE        = NO
+EXTRACT_STATIC         = YES
+EXTRACT_LOCAL_CLASSES  = YES
+HIDE_UNDOC_MEMBERS     = NO
+SOURCE_BROWSER         = YES
+INLINE_SOURCES         = NO
+STRIP_CODE_COMMENTS    = NO
+REFERENCED_BY_RELATION = YES
+REFERENCES_RELATION    = YES
+REFERENCES_LINK_SOURCE = YES
+
+# ── Build options ────────────────────────────────────────────────────────────
+JAVADOC_AUTOBRIEF      = YES
+QT_AUTOBRIEF           = NO
+MARKDOWN_SUPPORT       = YES
+AUTOLINK_SUPPORT       = YES
+BUILTIN_STL_SUPPORT    = YES
+DISTRIBUTE_GROUP_DOC   = YES
+GROUP_NESTED_COMPOUNDS = YES
+SUBGROUPING            = YES
+INLINE_GROUPED_CLASSES = NO
+INLINE_SIMPLE_STRUCTS  = NO
+TYPEDEF_HIDES_STRUCT   = NO
+EXTENSION_MAPPING      = h=C++ hpp=C++
+
+# ── Warnings ─────────────────────────────────────────────────────────────────
+QUIET                  = NO
+WARNINGS               = YES
+WARN_IF_UNDOCUMENTED   = NO
+WARN_IF_DOC_ERROR      = YES
+WARN_IF_INCOMPLETE_DOC = YES
+WARN_NO_PARAMDOC       = NO
+WARN_AS_ERROR          = NO
+WARN_FORMAT            = "$file:$line: $text"
+WARN_LOGFILE           = doc/doxygen/doxygen-warnings.log
+
+# ── HTML output ──────────────────────────────────────────────────────────────
+GENERATE_HTML          = YES
+HTML_OUTPUT            = html
+HTML_FILE_EXTENSION    = .html
+HTML_COLORSTYLE        = LIGHT
+HTML_COLORSTYLE_HUE    = 220
+HTML_COLORSTYLE_SAT    = 100
+HTML_COLORSTYLE_GAMMA  = 80
+HTML_TIMESTAMP         = NO
+HTML_DYNAMIC_SECTIONS  = YES
+GENERATE_TREEVIEW      = YES
+DISABLE_INDEX          = NO
+ENUM_VALUES_PER_LINE   = 1
+TREEVIEW_WIDTH         = 280
+EXT_LINKS_IN_WINDOW    = NO
+SEARCHENGINE           = YES
+SERVER_BASED_SEARCH    = NO
+
+# ── Disabled outputs (we only want HTML) ─────────────────────────────────────
+GENERATE_LATEX         = NO
+GENERATE_RTF           = NO
+GENERATE_MAN           = NO
+GENERATE_XML           = NO
+GENERATE_DOCBOOK       = NO
+GENERATE_AUTOGEN_DEF   = NO
+GENERATE_PERLMOD       = NO
+
+# ── Preprocessor ─────────────────────────────────────────────────────────────
+ENABLE_PREPROCESSING   = YES
+MACRO_EXPANSION        = YES
+EXPAND_ONLY_PREDEF     = YES
+SEARCH_INCLUDES        = YES
+INCLUDE_PATH           = code/include
+PREDEFINED             = CGAL_DISABLE_GMP \
+                         CGAL_DISABLE_MPFR \
+                         DOXYGEN_RUNNING
+
+# ── Diagrams ─────────────────────────────────────────────────────────────────
+HAVE_DOT               = NO
+CLASS_GRAPH            = YES
+COLLABORATION_GRAPH    = NO
+GROUP_GRAPHS           = YES
+INCLUDE_GRAPH          = NO
+INCLUDED_BY_GRAPH      = NO
+CALL_GRAPH             = NO
+CALLER_GRAPH           = NO
+
+# ── Aliases (CGAL-style) ─────────────────────────────────────────────────────
+ALIASES               += "concept{1}=\xrefitem concept \"Concept\" \"Concepts\" \1"
+ALIASES               += "models{1}=\xrefitem models \"Models\" \"Models\" \1"
+ALIASES               += "cgalRequires{1}=\par Requirements: \n\1"
+ALIASES               += "cgalParam{2}=\param \1 \2"