[Bughunt Phase 4] Documentation rebuild: chatbot artifacts in README, dead autotools guide, no published API reference

[grzanka]

Found during a full bughunt/architecture review. Grouped as one phase since it's almost entirely writing/editing docs and can proceed in parallel with the code-focused phases (#290–#293).

README.md

• Contains an unedited LLM authoring artifact: "Here is the updated documentation with proper header levels, maintaining clarity and structure." immediately before the Linux installation section
• Ends the uninstall section with a chatbot prompt shipped as documentation: "Would you like an automated uninstall script for easier removal? 🚀"
• Section numbering skips: options are labelled i, ii, iii, iv, then jumps to vi — there is no "v.", and the intro text says "for option (iv)-(vi)"
• Points to /docs/libamtrackManual.pdf under "Where do I find documentation" — no PDF exists anywhere in the repository (tracked separately as Include manual of PDF in the release files #124)
• Documents the Windows CMake flag as -DGETOPT_LIBRARY=..., but CMakeLists.txt:108 actually reads GETOPT_LIB — the documented flag name is silently ignored
• Lists libtool and gfortran as Linux/MSYS2 requirements — neither is used anywhere in the current CMake build; also describes the project as "ANSI C" while CMakeLists.txt:102 requires target_compile_features(amtrack PUBLIC c_std_11)
• Should link the Docusaurus documentation site (this is already tracked as Add in readme link to main documentation website #268 — cross-referencing here so it's done as part of the same README pass rather than separately)

README_DEVELOPERS (581 lines) describes a build system that no longer exists

Every section describes an autotools workflow (configure.ac, Makefile.am, m4/, aclocal.m4, INSTALL) — none of these files exist anywhere in the tree; the project has been CMake-only for some time. It also references SVN and SourceForge (the project is on GitHub/Git), Eclipse 3.6+ as the recommended IDE, OS X 10.10 "Mountain Lion" and XCode 6.3.2, and CRAN packaging steps for a package removed from CRAN in 2019. A new contributor following this file literally cannot build the project.

• Replace with a short, current CONTRIBUTING.md covering the actual CMake-based workflow (clone → cmake .. → cmake --build . → ctest, once [Bughunt Phase 1] CI cannot currently fail on a correctness regression: no assertions, no sanitizer job, no warning budget #291 lands), code style (.clang-format/pre-commit, already correctly documented in docs/manual/PreCommitSetup.md), and PR expectations. Delete README_DEVELOPERS rather than patch it piecemeal — it's cheaper to write 40 accurate lines than fix 581 stale ones.

Community/metadata files

• No CITATION.cff — a meaningful gap for scientific software that researchers are expected to cite in publications
• No SECURITY.md (relevant given the parser hardening in [Bughunt Phase 2] Memory safety: SPC binary-file decoder has unchecked file-controlled lengths and unbounded table fills #292)
• No CODE_OF_CONDUCT.md
• NEWS is placeholder joke text: "Keine Ahnung, was gibt's Neues? / Machst Du mirn Mettbrötchen? / TODO" — either populate or delete
• ChangeLog's last real entry is 0.6.2 (2015-06-26); the repo's git tags reach 0.10.x and beyond — either regenerate from tags/releases or delete it so it stops being actively misleading
• 65 source files' GPL header comments say "see file: copying.txt" but the actual file is COPYING (case and name both differ) — a one-shot sed across src/*.c

Doxygen / API reference

• Doxyfile's INPUT for pictures uses a Windows-style path (docs\manual\pictures), which Doxygen silently skips on Linux/macOS CI runners
• Several Doxyfile tags are flagged obsolete by the current Doxygen version; PAPER_TYPE has an invalid enum value; PROJECT_NUMBER is empty (should be wired to the CMake-derived version)
• include/AT_SPC.h:66 documents an undefined enum (Documentation for undefined enum 'spc' found)
• EXTRACT_ALL=YES in Doxyfile suppresses Doxygen's own undocumented-symbol warnings, so real documentation coverage is currently unmeasured. Separately, of the doc comments that do exist: 93 have a body that is literally just TODO, and 149 @param entries are documented only as TODO. Worst-affected headers: AT_KatzModel_Implementation.h (21 empty bodies), AT_SPC.h (14), AT_RDD_ExtendedTarget.h (14), AT_RDD_Simple.h (10), AT_Error.h (9). This overlaps Extend documentation of RDD models  #125 ("Extend documentation of RDD models").
• Doxygen is never run in CI and its HTML output is never published anywhere — the entire documentation strategy for a 382-function public API is currently "read the header comments on GitHub." Fix the Doxyfile issues above, add a CI job that builds it with -Werror-equivalent warning treatment (once coverage is above some floor), and publish the output — either to GitHub Pages from this repo or as a new section on the libamtrack.github.io Docusaurus site (that repo currently documents almost exclusively the Python wrapper, pyamtrack, with a single "read the headers" landing page for the C library)
• Build the LaTeX manual (docs/manual/libamtrackManual.tex) to PDF in CI and attach it to GitHub releases (closes Include manual of PDF in the release files #124)

Acceptance criteria

• README.md has no AI-authorship artifacts, correct section numbering, and accurate flag names
• README_DEVELOPERS is replaced by a CONTRIBUTING.md matching the actual CMake build
• CITATION.cff exists and validates
• Doxygen builds cleanly in CI and its output is reachable from a public URL

Related: #124, #125, #268