Here is a list of all documented concepts with brief descriptions:

[detail level 123]

Njh
Nconcepts	Behavioral concept namespace of the JH Toolkit
Rclosable_container_for	Concept checking whether a container `C` can be directly constructed ("closed") from a range `R`
Rcollectable_container_for	Concept verifying that a container `C` can collect elements from a range `R` via incremental insertion
Ris_contiguous_reallocable	Concept that constrains types usable in contiguous, reallocating containers
Rhas_std_hash	Checks whether `std::hash<T>` is valid and callable
Rhas_adl_hash	Checks whether a free (ADL-discoverable) `hash()` function exists
Rhas_mbr_hash	Checks whether a type defines a `hash()` member function
Rextended_hashable	Concept for types that can be hashed through any supported mechanism
Rindirectly_readable	Concept for types that can be read indirectly via dereference
Rindirectly_writable	Concept for types that support indirect write operations through dereference
Ris_iterator	Concept for detecting iterator-like types based on behavior
Rsentinel_for	Concept for detecting sentinel-iterator compatibility
Rinput_iterator	Concept for readable, comparable single-pass iterators
Routput_iterator	Concept for writable single-pass iterators
Rforward_iterator	Concept for multi-pass, readable, and self-sentinel iterators
Rbidirectional_iterator	Concept for iterators supporting bidirectional traversal
Rrandom_access_iterator	Concept for iterators supporting random access operations
Rbasic_lockable	Concept for basic lockable objects
Rexcl_lockable	Concept for exclusive lockable objects supporting try semantics
Rtimed_excl_lockable	Concept for timed exclusive lockable objects
Rshared_lockable	Concept for shared (reader) lockable objects
Rtimed_shared_lockable	Concept for shared lockables supporting timed acquisition
Rmutex_like	General mutex-like concept
Rtimed_mutex_like	Timed variant of `mutex_like`
Rrw_mutex_like	Read-write (RW) mutex concept
Rrecursive_mutex	Concept for counting reentrant (recursive) mutexes
Rreentrant_mutex	Concept for idempotent (structurally reentrant) mutexes
Rreentrance_capable_mutex	Concept for any mutex supporting some form of reentrance
Rvis_function_for	Concept describing the visual relation between a range and a callable
Rsequence	Concept that checks whether a type provides at least const (non-destructive) iteration
Rtuple_like	Concept recognizing tuple-like types
Rpair_like_for	Checks whether a type `P` is a 2-element tuple-like whose element types exactly match `K` and `V` (after remove_cvref)
Nmeta	Aggregated entry point for compile-time metaprogramming utilities
Rany_char	Concept representing character-semantic 1-byte integral types
Rtransparent_key	Concept checking whether key conversion through `key_traits<K>` is valid
Rcheck_all	Compile-time predicate applied to all alternatives in a variant
Npod	Aggregated entry point for Plain-Old-Data and layout-stable value utilities
Rstd_uint	Internal constraint for native unsigned integer types
Rtrivial_bytes	Concept for trivially layout-compatible types (POD-compatible memory view)
Rpod_like	Concept for types that are safe to treat as plain old data (POD)
Rcv_free_pod_like	Concept for POD-like types that are free of `const` or `volatile` qualification
Rstreamable	Checks whether a type can be streamed to `std::ostream`
Rstreamable_pod	Debug-only constraint for POD-like types printable to `std::ostream`
Ntyped	Aggregated entry point for lightweight typing and semantic placeholder utilities
Rmonostate_t	Concept: satisfied only if T is `monostate`
Rimmutable_str_compatible	Concept for types compatible with `jh::immutable_str`