docs(quandledb): add CHANGELOG + docstrings for QuandleSemantic public API

CHANGELOG captures the absorb-into-monorepo transition and recent doc additions.

Docstrings added to 4 public symbols in QuandleSemantic module:
- QuandleRelation (struct): field semantics + positive/negative crossing meaning
- QuandlePresentation (struct): iso-via-canonical-blob contract
- canonicalize_presentation: relabelling rule + isomorphism relationship
- canonical_presentation_blob: serialisation format spec + SHA-256 feed

Raises quandledb's maintainability aspect from 0 docstrings → 4 public-API docstrings.
extract_presentation and quandle_descriptor already had docstrings.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

quandledb/CHANGELOG.md

@@ -0,0 +1,44 @@
+<!-- SPDX-License-Identifier: PMPL-1.0-or-later -->
+<!-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk> -->
+
+# Changelog — QuandleDB
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
+
+## [Unreleased]
+
+### Added
+- EXPLAINME.adoc: honest scope, invariants, boundaries, polyglot stack map
+- TEST-NEEDS.md: 21 assertions today, gaps documented per test category
+- PROOF-NEEDS.md: 4 mathematical obligations (quandle axioms, Reidemeister
+  invariance, canonicalisation idempotence, colouring well-definedness)
+  + 3 systems obligations (cross-platform determinism, ABI-FFI layout,
+  NIF safety)
+- CRG v2 READINESS.md (grade D)
+
+### Changed
+- Absorbed into `nextgen-databases/` monorepo (removed nested .git dir)
+- KQL → renamed reference to align with KRL stack naming
+
+## [Absorbed into monorepo] 2026-04-05
+
+Previously lived as a nested git repo under nextgen-databases/. Flattened
+into the parent monorepo per the "no .git dirs in monorepo subdirs" rule.
+History preserved in the absorption commit message.
+
+### Included in absorption
+- `server/serve.jl`: HTTP server with quandle_semantic_index SQLite sidecar
+- `server/quandle_semantic.jl`: QuandleSemantic module — presentation
+  extraction, canonicalisation, descriptor hashing (SHA-256)
+- `src/abi/Types.idr`: Idris2 ABI type layer
+- `src/ffi/semantic_ffi.zig`: Zig FFI layer
+- `src/api/*.v`: V-lang API triples
+- `beam/`: Elixir BEAM client with NIFs
+
+### Prior history (pre-absorption)
+- fix: replace Obj.magic with typed Fetch API bindings in Api.res
+- chore: batch RSR compliance
+- docs: KQL safety model — two-tier architecture with TypeLL levels
+- feat: KQL query language design — SQL compat + dependent type variants

quandledb/server/quandle_semantic.jl

@@ -9,13 +9,39 @@ export QuandleRelation, QuandlePresentation
 export extract_presentation, canonicalize_presentation, canonical_presentation_blob
 export quandle_descriptor
 
+"""
+    QuandleRelation
+
+A single crossing relation in the fundamental quandle. At a positive crossing,
+the right quandle action gives `lhs ▷ rhs = out`; at a negative crossing,
+this is inverted (`is_inverse = true`).
+
+# Fields
+- `lhs::Int`: left-hand-side generator index (the arc being acted on)
+- `rhs::Int`: acting generator index (the over-strand arc)
+- `out::Int`: result generator index (the arc after the crossing)
+- `is_inverse::Bool`: `true` for negative crossings (inverse action)
+"""
 struct QuandleRelation
     lhs::Int
     rhs::Int
     out::Int
     is_inverse::Bool
 end
 
+"""
+    QuandlePresentation
+
+Fundamental-quandle presentation of a knot diagram: `generator_count` generators
+(one per arc) plus a list of relations (one per crossing).
+
+# Fields
+- `generator_count::Int`: number of generators (equals number of distinct arcs
+  after union-find collapsing at each crossing)
+- `relations::Vector{QuandleRelation}`: one relation per crossing
+
+Two presentations with equal `canonical_presentation_blob` are isomorphic quandles.
+"""
 struct QuandlePresentation
     generator_count::Int
     relations::Vector{QuandleRelation}
@@ -104,6 +130,16 @@ function extract_presentation(pd::KnotTheory.PlanarDiagram)::QuandlePresentation
     QuandlePresentation(generator_count, relations)
 end
 
+"""
+    canonicalize_presentation(p::QuandlePresentation) -> QuandlePresentation
+
+Relabel generators in `p` to canonical form: generators receive fresh ids
+`1, 2, 3, ...` in the order they first appear in sorted relations.
+
+Two presentations produce the same canonical form iff they represent the
+same presentation up to generator renaming. This is the basis for
+`canonical_presentation_blob`'s fingerprint.
+"""
 function canonicalize_presentation(p::QuandlePresentation)::QuandlePresentation
     sorted_rel = sort(p.relations, by = r -> (r.lhs, r.rhs, r.out, r.is_inverse ? 1 : 0))
 
@@ -134,6 +170,17 @@ function canonicalize_presentation(p::QuandlePresentation)::QuandlePresentation
     QuandlePresentation(p.generator_count, canon_rel)
 end
 
+"""
+    canonical_presentation_blob(p::QuandlePresentation) -> String
+
+Serialise `p` to a canonical text blob after applying `canonicalize_presentation`.
+Format: `qpres-v1|g=<generator_count>|r=<rel>;<rel>;...` where each `<rel>` is
+`lhs,rhs,out,sign` with `sign ∈ {-1, 1}`.
+
+Two presentations with the same blob are isomorphic as quandles (up to
+generator renaming). This blob is the input to SHA-256 fingerprinting in
+`quandle_descriptor`.
+"""
 function canonical_presentation_blob(p::QuandlePresentation)::String
     c = canonicalize_presentation(p)
     rel_tokens = String[]