feat(quasicryth-research): direct C→Rust transcode + COW radix trie variant

Cargo.toml

@@ -47,6 +47,14 @@ exclude = [
     # Kept out of the workspace so the nondeterministic autoencoder never
     # enters the deterministic lance-graph compile path (determinism boundary).
     "crates/lance-graph-arm-discovery",
+    # Quasicryth algebraic-core transcode (Tacconelli 2026, arxiv 2603.14999) —
+    # standalone zero-dep research/testing crate. Verifies the workspace's
+    # φ-substrate decisions (bgz17 17φ/11, helix golden-spiral, jc::weyl) against
+    # the reference algebra. NOT a production compressor: covers only the
+    # algebraic core (tilings + hierarchy + deep-position detection), not the
+    # arithmetic-coding / LZMA-escape / tokenizer pipeline.
+    # Verified via `cargo test --manifest-path crates/quasicryth-research/Cargo.toml`.
+    "crates/quasicryth-research",
 ]
 resolver = "2"
 

crates/quasicryth-research/.gitignore

@@ -0,0 +1,2 @@
+/target
+Cargo.lock

crates/quasicryth-research/Cargo.toml

@@ -0,0 +1,26 @@
+[package]
+name = "quasicryth-research"
+version = "0.1.0"
+edition = "2021"
+license = "Apache-2.0"
+publish = false
+description = "Direct Rust transcode of the algebraic core of Quasicryth (Tacconelli 2026, arxiv 2603.14999) — Fibonacci quasicrystal tilings, substitution hierarchy, deep n-gram position detection. Research/testing crate, NOT a production compressor."
+
+# Standalone codec constitution (matches helix / bgz17 / deepnsm): the default
+# build is ZERO dependencies. Algebraic core only — no arithmetic coding, no
+# LZMA escape, no tokenization, no codebook construction (those live in the
+# upstream C reference implementation and are out of scope for this transcode).
+#
+# Upstream: https://github.com/robtacconelli/quasicryth (MIT/Apache, v5.6.0).
+# This transcode covers fib.h / fib.c (598 LOC) + the algebraic types from
+# qtc.h. Paper proves five theorems (non-collapse, PV-property, Sturmian
+# minimality, Golden Compensation, bounded overhead) — the included tests
+# verify all five on synthetic data.
+[dependencies]
+
+[dev-dependencies]
+
+# Empty [workspace] so cargo treats this crate as standalone when invoked via
+# --manifest-path. Listed under the root Cargo.toml `exclude` so workspace-wide
+# commands never pull it into the deterministic main compile graph.
+[workspace]

crates/quasicryth-research/README.md

@@ -0,0 +1,180 @@
+# quasicryth-research
+
+Direct Rust transcode of **Quasicryth** (Tacconelli 2026,
+[arxiv 2603.14999](https://arxiv.org/abs/2603.14999), upstream
+[github.com/robtacconelli/quasicryth](https://github.com/robtacconelli/quasicryth)
+v5.6.0).
+
+**Purpose:** research and testing. Two goals:
+
+1. Validate the workspace's φ-substrate decisions (bgz17's `17φ/11`, helix's
+   golden-spiral hemisphere) against the reference algebra — without
+   depending on the upstream C build.
+2. Demonstrate the **codebook architecture in two variants** behind one
+   trait: the original flat storage shape from the C reference, and a
+   COW Adaptive Radix Tree variant that fits the workspace's append-only
+   substrate doctrine.
+
+## What's transcoded
+
+| Phase | Upstream C | Rust module | Status | Tests |
+|---|---|---|---|---|
+| 0 | `fib.c` + types from `qtc.h` | `tiling`, `hierarchy`, `constants`, `types` | shipped | 19 unit + 9 paper-theorem integration |
+| 1 | `md5.c` + `tok.c` (partial) | `md5`, `tok` | shipped | 8 RFC-1321 vectors + 12 tokenizer round-trips |
+| 2 | `cb.c` (algorithmic shape) | `codebook` (FlatCodebook + CowRadixCodebook) | shipped | 8 codebook tests, cross-variant validation |
+| 3 | `ac.c` | `arith_coder` (Model256, VModel, Encoder, Decoder) | shipped | 9 round-trip tests at multiple scales |
+| 4 | `compress.c` + `decompress.c` (simplified) | `pipeline` (compress/decompress) | shipped | 11 round-trip tests covering both variants |
+| 5 | integration | `tests/round_trip.rs` + `tests/paper_theorems.rs` | shipped | 7 cross-variant integration tests |
+| 6 | `main.c` | `bin/qresearch.rs` | shipped | CLI: compress / decompress / round-trip |
+
+**Total tests: 83 passing.** Zero dependencies. No `unsafe`. Stable Rust.
+
+## What this is NOT
+
+The Rust pipeline is **NOT byte-compatible** with the upstream `.qm56`
+format. The full v5.6 production compressor ships:
+
+- multi-level adaptive arithmetic coding with 144 specialised level
+  context models + 12 per-index models + recency caches + two-tier
+  unigram model + word-level LZ77,
+- 36-tiling greedy selection per block,
+- LZMA escape stream for OOV words,
+- frequency-counter pruning for memory bounds on large inputs,
+- multi-level n-gram codebooks (3-gram through 144-gram).
+
+The Rust pipeline here is **simplified to a single-tier (unigram)
+encoding** so the codebook trait abstraction is the clean variation
+point and the COW radix trie variant is exercised end-to-end. Multi-tier
+n-gram encoding is a phase 5+ extension. The Fibonacci tiling +
+substitution hierarchy + deep-position detection are verified to
+satisfy the paper's five core theorems (see
+`tests/paper_theorems.rs`), but the bit-stream itself only encodes
+word-ID symbols at the unigram tier.
+
+The Rust pipeline **round-trips with itself**: `decompress(compress(x))
+== x` for every test input under both `Variant::Flat` and
+`Variant::CowRadix`. This is the property the integration tests verify.
+
+## Verification
+
+```bash
+# All 83 tests:
+cargo test --manifest-path crates/quasicryth-research/Cargo.toml
+
+# Paper-theorem suite only (the original 9 algebraic claims):
+cargo test --manifest-path crates/quasicryth-research/Cargo.toml \
+  --test paper_theorems
+
+# Cross-variant integration suite (Phase 5):
+cargo test --manifest-path crates/quasicryth-research/Cargo.toml \
+  --test round_trip
+```
+
+Lint discipline:
+
+```bash
+cargo clippy --manifest-path crates/quasicryth-research/Cargo.toml \
+  --all-targets -- -D warnings
+cargo fmt --manifest-path crates/quasicryth-research/Cargo.toml --check
+```
+
+Both clean.
+
+## CLI
+
+```bash
+cargo build --release --manifest-path crates/quasicryth-research/Cargo.toml \
+  --bin qresearch
+./crates/quasicryth-research/target/release/qresearch round-trip /path/to/file.txt
+./crates/quasicryth-research/target/release/qresearch round-trip -v cow /path/to/file.txt
+./crates/quasicryth-research/target/release/qresearch compress -v flat in.txt out.qrs1
+./crates/quasicryth-research/target/release/qresearch decompress out.qrs1 in.txt.recovered
+```
+
+The `round-trip` subcommand compresses to memory, decompresses, and
+verifies identity — useful for quick fuzz-style validation on real text.
+
+## Paper-theorem verification (algebraic substrate)
+
+Tests in `tests/paper_theorems.rs` verify, on synthetic L/S sequences:
+
+- **Thm 2** Fibonacci hierarchy never collapses (both L and S supertiles persist).
+- **Cor 4** Period-5 collapses by level 4 or 5 (vs Fibonacci's unbounded depth).
+- **Thm 9** Golden Compensation: L:S ratio = φ at every level.
+- **Thm 13/Cor 15** Aperiodic advantage grows with scale.
+- **Sturmian** Factor complexity ≤ n+1 (the minimality property that
+  gives maximal codebook efficiency, Thm 7).
+
+Plus algebraic and structural invariants: PV-property (φ² = φ+1),
+`HIER_WORD_LENS = F_3..F_12`, no-adjacent-S on all 36 canonical tilings.
+
+## Codebook variants
+
+| Property | `FlatCodebook` | `CowRadixCodebook` |
+|---|---|---|
+| Storage | flat `Vec<u32>` per tier + `HashMap` for lookup | Adaptive Radix Tree (Node4 / Node16 / Node256) per tier |
+| Build cost | O(n log n) — frequency sort | O(n log n) sort + O(n · key_len) trie inserts |
+| Lookup | O(1) average (HashMap) | O(key_len) tree walk |
+| Memory | dense | sparse, shared across versions (Arc) |
+| Versioning | no | **path-copy COW** — every insert returns a new root, prior roots stay valid |
+| Append-only | no | **yes** — fits the workspace's substrate doctrine |
+| Threading | `Send + Sync` (immutable post-build) | `Send + Sync` (Arc-shared subtrees, immutable) |
+
+Both implement the `Codebook` trait. The `pipeline::Variant` enum
+picks between them. Tests validate equivalence: under identical
+inputs, both produce the same `compress → decompress` output.
+
+The COW property is **explicitly exercised** in
+`codebook::tests::cow_art_path_copy_preserves_old_root` — `art_v0`
+stays empty after `art_v1.insert(...)` and `art_v2.insert(...)`;
+each version sees only its own inserts. This is the architectural
+property the workspace's append-only doctrine requires.
+
+## Compressed stream format (v1)
+
+The Rust pipeline writes a self-contained format with the magic
+`QRS1` ("Quasicryth Research Simplified v1"):
+
+```
+magic       : [4]  "QRS1"
+orig_size   : u64  little-endian
+n_tokens    : u32
+n_words     : u32
+n_unique    : u32
+lowered_size: u32
+lowered     : [u8; lowered_size]   the lowered byte stream
+spans       : [(u32 offset, u32 len, u8 case_flag); n_tokens]
+case_size   : u32
+case_data   : [u8; case_size]      AC over Model256 (token case flags)
+word_size   : u32
+word_data   : [u8; word_size]      AC over VModel (codebook indices)
+```
+
+This is **not** the upstream `.qm56` format — by design, see the
+"What this is NOT" section above.
+
+## Relationship to workspace crates
+
+- **bgz17** — uses `17φ/11 ≈ 5/2` (major tenth) as octave-stacking
+  constant for codebook hierarchy depth; this crate verifies the
+  non-collapse theorem that justifies φ over rational stacking
+  approximations.
+- **helix** — uses pure φ for golden-angle azimuth and `√u` for
+  equal-area hemisphere placement; this crate verifies the Sturmian
+  minimality that makes φ optimal among irrational slopes.
+- **jc::weyl** — proves 1-D `{k·φ⁻¹ mod 1}` star-discrepancy is
+  minimal at N=144 and N=1000; this crate's `qc_word_tiling`
+  exercises the same φ-stride at hierarchy scale.
+
+## Upstream
+
+`https://github.com/robtacconelli/quasicryth` — v5.6.0 as of the
+transcode date. The upstream is the canonical reference; this crate
+tracks its algebraic surface and pipeline shape only and does NOT
+attempt byte-for-byte compatibility with its compressed output.
+
+## Crate policy
+
+Standalone, zero-dependency, `exclude`d from the lance-graph
+workspace — same convention as `bgz17`, `deepnsm`, `helix`,
+`bgz-tensor`. Verified via `cargo test --manifest-path`.