docs: modernize doxygen build and publish from this repository

[baylesj]

Summary

The published API docs live in the separate jsoncpp-docs repo, last updated January 2021 for 1.9.4. The local doxygen build has also been broken since the versioning rework removed the top-level version file. This PR fixes the build, modernizes the output, and publishes docs from this repository via GitHub Pages so they can no longer rot.

Build fixes

• doxybuild.py reads the version from include/json/version.h instead of a version file that CMake only writes to the build dir.
• doc/doxyfile.in reduced to non-default settings (the 1.8.5-era template produced 17 obsolete-tag warnings on current doxygen) and now sets WARN_AS_ERROR = FAIL_ON_WARNINGS, so doc regressions fail CI.
• JSONCPP_DEPRECATED / JSON_API are stripped during preprocessing and __cplusplus=201703L is predefined, so deprecated members and the std::string_view overloads get documented.

Documentation fixes

• reader.h / writer.h: a mismatched 'settings_\`` quote opened a backtick span that swallowed the rest of each header — CharReaderBuilderandStreamWriterBuilder` were effectively undocumented on the published site.
• value.h: document the remaining params of Value::get / Value::removeMember.
• json_value.cpp: hide the private Value::CZString implementation with \cond.

Output

• Styled with doxygen-awesome-css v2.4.2 (vendored, MIT) instead of the 1.8.13-era header/footer; tree view and search enabled; auto dark mode.
• README.md is the main page; jsoncpp.dox becomes a "Quick start" page with dead SourceForge links removed. Dropped the 3-line roadmap.dox and the redundant web_doxyfile.in.

Publishing

• New docs workflow: builds on PRs (warning check only) and deploys to GitHub Pages on pushes to master, using a pinned, checksum-verified doxygen 1.18.0. README links point at https://open-source-parsers.github.io/jsoncpp/.

Test plan

• python3 doxybuild.py on macOS with doxygen 1.18.0: exit 0, empty warning log (previously 66 warning lines).
• Verified in generated HTML: README renders as main page (GitHub [!NOTE] alert renders as a doxygen note), Quick start page present, settings_ docs restored on both builders, deprecated getFormatedErrorMessages documented, string_view overloads shown, CZString absent.
• clang-format --dry-run --Werror clean on touched C++ files; -fsyntax-only passes (changes are comment-only).
• docs workflow build job passes on this PR.
• After merge: deploy job publishes to https://open-source-parsers.github.io/jsoncpp/ (Pages has been enabled with source "GitHub Actions"); then redirect + archive jsoncpp-docs.

[coveralls]

Coverage Report for CI Build 32424602421

Coverage remained the same at 89.907%

Details

• Coverage remained the same as the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	2740
Covered Lines:	2615
Line Coverage:	95.44%
Relevant Branches:	2640
Covered Branches:	2222
Branch Coverage:	84.17%
Branches in Coverage %:	Yes
Coverage Strength:	23828.01 hits per line

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💛 - Coveralls

[greptile-apps]

Greptile Summary

The PR modernizes JsonCpp’s Doxygen configuration and publishes generated API documentation through GitHub Pages.

• Reads the project version from include/json/version.h and repairs documentation tarball generation.
• Adds a warning-enforcing documentation build and a master-only Pages deployment workflow.
• Updates API comments, documentation links, and presentation using vendored Doxygen styling.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains; the deployment is now restricted to master, and the documentation tarball no longer references the deleted version or NEWS files.

Important Files Changed

Filename	Overview
.github/workflows/docs.yml	Adds pinned documentation build and Pages deployment jobs; the current ref guard restricts publishing to master.
doxybuild.py	Sources the version from the public version header, improves warning reporting, and removes nonexistent tarball inputs.
doc/doxyfile.in	Replaces the obsolete generated template with a concise modern Doxygen configuration that enables strict warnings and themed HTML output.
include/json/reader.h	Repairs documentation markup so reader builder documentation renders correctly.
include/json/value.h	Completes parameter documentation for existing Value APIs.
include/json/writer.h	Repairs documentation markup so writer builder documentation renders correctly.
src/lib_json/json_value.cpp	Excludes the private CZString implementation from generated public documentation.

Sequence Diagram

sequenceDiagram
    participant Trigger as Push / PR / Manual Trigger
    participant Build as Documentation Build
    participant Artifact as Pages Artifact
    participant Deploy as Pages Deployment
    Trigger->>Build: Run docs workflow
    Build->>Build: Generate Doxygen HTML
    Build->>Artifact: Upload generated site
    alt ref is master
        Artifact->>Deploy: Deploy to GitHub Pages
    else ref is not master
        Artifact-->>Trigger: Build check only
    end

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