Use one-line module docstrings in the API checker scripts

Codacy runs two docstring checkers with opposite rules for module
docstrings: with the summary on the first line it reported D213, with
the summary on the second line it reports D212. A one-line docstring
satisfies both. Keep the summary as the docstring and move the details
into a comment below it; nothing reads the module docstrings.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

tools/api_checker/check_docs.py

@@ -1,12 +1,10 @@
 #!/usr/bin/env python3
-"""
-Verify that public API entries have documentation links.
+"""Verify that public API entries have documentation links."""
 
-Consumes an API snapshot from extract_api.py and checks:
-1. Every public callable/type-tier entry has an @sa comment (with exceptions)
-2. Every @sa URL resolves to an existing documentation file
-3. No @sa comments appear on non-public entities
-"""
+# Consumes an API snapshot from extract_api.py and checks:
+# 1. Every public callable/type-tier entry has an @sa comment (with exceptions)
+# 2. Every @sa URL resolves to an existing documentation file
+# 3. No @sa comments appear on non-public entities
 
 import argparse
 import json

tools/api_checker/check_macros.py

@@ -1,16 +1,14 @@
 #!/usr/bin/env python3
-"""
-Advisory-only cross-check between documented macros and their #define sites.
+"""Advisory-only cross-check between documented macros and their #define sites."""
 
-Macros have no C++ access-specifier concept, so the AST-based public/private test that
-extract_api.py uses for classes doesn't transfer -- see tools/api_checker/POLICY.md's "Known
-limitations" section. This script only checks one direction: that every macro documented under
-docs/mkdocs/docs/api/macros/ still has a matching #define somewhere under include/nlohmann/,
-catching stale or renamed doc pages. It does NOT check the converse (undocumented macros) --
-no reliable signal exists for that direction given this codebase's conventions.
-
-Never blocks CI -- always exits 0, even when it reports findings.
-"""
+# Macros have no C++ access-specifier concept, so the AST-based public/private test that
+# extract_api.py uses for classes doesn't transfer -- see tools/api_checker/POLICY.md's "Known
+# limitations" section. This script only checks one direction: that every macro documented under
+# docs/mkdocs/docs/api/macros/ still has a matching #define somewhere under include/nlohmann/,
+# catching stale or renamed doc pages. It does NOT check the converse (undocumented macros) --
+# no reliable signal exists for that direction given this codebase's conventions.
+#
+# Never blocks CI -- always exits 0, even when it reports findings.
 
 import argparse
 import glob

tools/api_checker/diff_api.py

@@ -1,26 +1,24 @@
 #!/usr/bin/env python3
-"""
-Diff the public API surface between two refs to flag breaking vs. feature changes.
+"""Diff the public API surface between two refs to flag breaking vs. feature changes."""
 
-A "ref" for --old/--new is resolved in this order:
-1. A stored, committed historical record at tools/api_checker/history/<ref>.json, if one exists
-   and --no-history wasn't passed (fast path -- no libclang/git-archive needed).
-2. Live extraction: check the ref out via `git archive` into a temp dir and run extract_api.py
-   against it (needed for HEAD, branches, or any tag not yet backfilled into history/).
---old-file/--new-file bypass both and load an arbitrary surface JSON file directly.
-
-Uses extract_api.py's --surface-output (identity-only: scope, kind, name, identity_name, tier,
-signature, pretty_signature -- no location, no doc_url) for both sides, so the diff reflects only
-genuine API changes, never unrelated code motion or documentation-site restructuring. Identity is
-(scope, identity_name, kind, signature) -- see extract_api.py's identity_key()/get_signature_text()
-docstrings for the full history of why this is what it is: a naive {scope,name,kind,params} key
-silently collided on overloads differing only by constness/SFINAE; switching to libclang's USR
-fixed that but encoded the *enclosing class template's own arity* into every member's identity, so
-a single backward-compatible template-parameter addition (confirmed via real release tags
-v3.11.2->v3.11.3) made ~228 of 330 entries look "changed" for a release with no real breaking
-changes. The current raw-source-text-signature approach was arrived at, and each of several further
-refinements verified, by testing against real historical releases -- not by inspecting code alone.
-"""
+# A "ref" for --old/--new is resolved in this order:
+# 1. A stored, committed historical record at tools/api_checker/history/<ref>.json, if one exists
+#    and --no-history wasn't passed (fast path -- no libclang/git-archive needed).
+# 2. Live extraction: check the ref out via `git archive` into a temp dir and run extract_api.py
+#    against it (needed for HEAD, branches, or any tag not yet backfilled into history/).
+# --old-file/--new-file bypass both and load an arbitrary surface JSON file directly.
+#
+# Uses extract_api.py's --surface-output (identity-only: scope, kind, name, identity_name, tier,
+# signature, pretty_signature -- no location, no doc_url) for both sides, so the diff reflects only
+# genuine API changes, never unrelated code motion or documentation-site restructuring. Identity is
+# (scope, identity_name, kind, signature) -- see extract_api.py's identity_key()/get_signature_text()
+# docstrings for the full history of why this is what it is: a naive {scope,name,kind,params} key
+# silently collided on overloads differing only by constness/SFINAE; switching to libclang's USR
+# fixed that but encoded the *enclosing class template's own arity* into every member's identity, so
+# a single backward-compatible template-parameter addition (confirmed via real release tags
+# v3.11.2->v3.11.3) made ~228 of 330 entries look "changed" for a release with no real breaking
+# changes. The current raw-source-text-signature approach was arrived at, and each of several further
+# refinements verified, by testing against real historical releases -- not by inspecting code alone.
 
 import argparse
 import json

tools/api_checker/extract_api.py

@@ -1,24 +1,22 @@
 #!/usr/bin/env python3
-"""
-Extract the public API surface of nlohmann/json using libclang AST.
+"""Extract the public API surface of nlohmann/json using libclang AST."""
 
-This tool derives the public API from C++ semantics (class templates, access specifiers,
-namespace scoping) independently of documentation status. The extracted surface is the
-source of truth for what is considered "public API" — doc-checking and API diffing are
-downstream consumers of this snapshot.
-
-Strategy:
-1. Parse include/nlohmann/json.hpp with libclang (with proper system includes)
-2. Walk the primary class-template definitions of the 6 known public classes
-3. Extract callable members (methods, constructors, destructors, conversion ops) and type aliases
-4. Extract free functions/operators in nlohmann:: (excluding detail::)
-5. Handle alias-exposed exception types by following the alias to the detail:: definition
-6. Normalize away the ABI inline-namespace (json_abi_v3_12_0, json_abi_diag_v3_12_0, etc.)
-7. Emit a snapshot with an overload-disambiguating identity key and documentation status
-
-Output includes both public_api (all tracked public entities) and documented_non_public
-(entities with @sa comments that are NOT in the public surface — used for validation).
-"""
+# This tool derives the public API from C++ semantics (class templates, access specifiers,
+# namespace scoping) independently of documentation status. The extracted surface is the
+# source of truth for what is considered "public API" — doc-checking and API diffing are
+# downstream consumers of this snapshot.
+#
+# Strategy:
+# 1. Parse include/nlohmann/json.hpp with libclang (with proper system includes)
+# 2. Walk the primary class-template definitions of the 6 known public classes
+# 3. Extract callable members (methods, constructors, destructors, conversion ops) and type aliases
+# 4. Extract free functions/operators in nlohmann:: (excluding detail::)
+# 5. Handle alias-exposed exception types by following the alias to the detail:: definition
+# 6. Normalize away the ABI inline-namespace (json_abi_v3_12_0, json_abi_diag_v3_12_0, etc.)
+# 7. Emit a snapshot with an overload-disambiguating identity key and documentation status
+#
+# Output includes both public_api (all tracked public entities) and documented_non_public
+# (entities with @sa comments that are NOT in the public surface — used for validation).
 
 import argparse
 import json

tools/api_checker/snapshot_release.py

@@ -1,14 +1,12 @@
 #!/usr/bin/env python3
-"""
-Capture immutable, per-release API surface records into tools/api_checker/history/.
+"""Capture immutable, per-release API surface records into tools/api_checker/history/."""
 
-These are the durable, committed counterpart to diff_api.py's live git-archive-and-extract path:
-once a release is tagged, run this once to capture tools/api_checker/history/<tag>.json, commit
-it, and future diffs against that tag hit the fast, no-libclang-needed stored-file path in
-diff_api.py automatically. See tools/api_checker/README.md's "Workflow: Release Checklist" and
-POLICY.md for the full policy (manual step, not CI-automated; files are immutable once committed
--- regenerate only via --force, and only as a deliberate, reviewed choice).
-"""
+# These are the durable, committed counterpart to diff_api.py's live git-archive-and-extract path:
+# once a release is tagged, run this once to capture tools/api_checker/history/<tag>.json, commit
+# it, and future diffs against that tag hit the fast, no-libclang-needed stored-file path in
+# diff_api.py automatically. See tools/api_checker/README.md's "Workflow: Release Checklist" and
+# POLICY.md for the full policy (manual step, not CI-automated; files are immutable once committed
+# -- regenerate only via --force, and only as a deliberate, reviewed choice).
 
 import argparse
 import datetime