feat(pattern): griff-pattern — the std-only structural algebra (S16 Phase 1)

Cargo.toml

@@ -1,5 +1,5 @@
 [workspace]
-members  = ["core", "ui-core", "cockpit", "cli", "plugin", "preview"]
+members  = ["core", "pattern", "ui-core", "cockpit", "cli", "plugin", "preview"]
 # `fuzz/` is an isolated nightly cargo-fuzz crate (ADR-0010); it is
 # deliberately not a workspace member so stable `--workspace` builds,
 # clippy, and tests never touch it.

docs/adr/0029-swang-authoring-and-verified-lifting.md

@@ -105,8 +105,11 @@ in [`../swang/spec.md`](../swang/spec.md); the delivery plan in
 
 2. **Two crates, one dependency direction.** `griff-pattern` is the pure
    structural algebra — **std-only: zero external dependencies, no
-   `griff-core`, no MIDI, no serde, no time types** — holding `Pattern`,
-   `PatternTree`, traversals, budgets, and deterministic pruning.
+   `griff-core`, no MIDI, no serde, no time types** — holding `Kernel`,
+   `Expansion`, `NodePath`, traversals, budgets, and deterministic pruning.
+   No materialized pattern tree exists: the expansion is answered per cell
+   from coordinate digits, and the tree stays implicit in the `NodePath`
+   addressing; the pruning semantics are unaffected.
    `griff-swang` holds the AST, parser/formatter (later phases), and the
    lowering into `griff-core` types. Serialization of artifacts lives in
    `griff-swang` or an adapter, never in `griff-pattern`.

docs/decisions.log.md

@@ -1688,3 +1688,16 @@ Architectural decisions go to [`adr/`](adr/) instead.
   Verus toolchain in CI, to achieve verification effort proportional to
   frozen semantics, accepting that no machine-checked functional proofs
   exist for v0.1. Logged in `process-backlog.md`.
+
+- 2026-07-14 — In the context of the `griff-pattern` Phase 1 review (#113),
+  facing a stage plan that promised a materialized `PatternTree` while the
+  implementation answers each cell of the final `Expansion` grid from its
+  coordinate digits, we decided for **recognizing the coordinate-digit
+  evaluator as the v0.1 representation** — the tree stays implicit in the
+  `NodePath` addressing — and against building the intermediate tree to match
+  the document, to achieve the same normative pruning semantics without the
+  exponential intermediate allocation, accepting that a future phase needing
+  the explicit tree (recognizers, lifting) must introduce it then. `thin` is
+  likewise deferred out of Phase 1: spec §1.10 fixes its type contract, but
+  its cell-selection rule is unspecified, and inventing one to satisfy an
+  acceptance checkbox would freeze semantics nobody designed.

docs/stages/S16-swang-language-and-verified-lifting.md

@@ -115,9 +115,13 @@ Specified and scheduled, with semantics in the spec:
 fractalize
 linearize
 map_rhythm
-thin
 ```
 
+`thin` sits between the tiers: its **type contract** is fixed (spec §1.10 —
+it may only flip `X -> .`, preserving dimensions and sequence length), but
+its cell-selection rule is deliberately unspecified and it ships in no phase
+until that rule earns its own spec section.
+
 Candidate roster — names under consideration, with **no promised semantics
 and no assigned delivery phase** until each earns its spec section:
 
@@ -279,23 +283,29 @@ No generation behavior changes.
 Add domain-neutral primitives, std-only:
 
 ```text
-Pattern / Cell
-PatternTree / NodePath
+Kernel / NodePath
+Expansion
 Traversal (row_major | snake)
 ActivitySequence
-FractalSpec / ExpansionBudget
+PruneSpec / DensityBps / ExpansionBudget
 ```
 
+There is deliberately **no materialized `PatternTree`**: `fractalize`
+answers each cell of the final `Expansion` grid from its coordinate digits
+(most-significant first — the digits *are* the implicit tree path), so the
+tree exists in the addressing scheme rather than in memory. The normative
+pruning semantics are unchanged; the intermediate representation of the
+first draft is simply not needed (decisions log 2026-07-14).
+
 Implement deterministic `fractalize`, traversal, and path-addressed pruning
 without MIDI, tonal, fretboard, UI, serde, or generator dependencies.
 
 Acceptance:
 
 - empty parents produce empty descendants;
-- expansion never exceeds the declared budget, and the breach error carries
-  the offending `NodePath`;
-- transforms are deterministic and compositional; `thin` preserves cell
-  count and sequence length;
+- expansion never exceeds the declared budget, and every breach error —
+  depth or cells — carries the offending `NodePath`;
+- transforms are deterministic and compositional;
 - two-dimensional kernels require explicit traversal; ragged kernels are
   rejected before allocation;
 - golden coordinate/activity vectors for both traversals; golden

docs/swang/spec.md

@@ -263,6 +263,9 @@ Consequences, all normative:
 
 - `thin : Pattern2D -> Pattern2D` may only flip `X -> .`. It preserves
   dimensions, cell count, coordinates, and post-`linearize` sequence length.
+  Only this type contract is fixed: the cell-selection rule is deliberately
+  unspecified, and `thin` ships in no phase until that rule earns its own
+  spec section.
 - Compaction (removing cells, shortening the sequence) is a **separate,
   deferred operator with a distinct output type** — returning a plain
   `ActivitySequence` from it would be a type-system lie.
@@ -403,7 +406,8 @@ griff generate seed.gp5 out.mid \
 3. A ragged kernel is rejected before expansion.
 4. `.` creates a gap in offsets; it does not disappear.
 5. Two adjacent `X` create two short notes.
-6. `thin` preserves cell count and sequence duration.
+6. The expansion artifact records the bar geometry (PPQN, meter,
+   `bar_duration`, `slots_per_bar`).
 7. `rest-pad` pads only the tail of the final bar.
 8. `reject` refuses an incomplete final bar.
 9. Pattern rhythm overrides corpus rhythm but not corpus novelty/gesture.

pattern/Cargo.toml

@@ -0,0 +1,22 @@
+[package]
+name         = "griff-pattern"
+description  = "Pure structural pattern algebra: kernels, bounded fractal expansion, traversals (S16)"
+version.workspace      = true
+edition.workspace      = true
+rust-version.workspace = true
+license.workspace      = true
+repository.workspace   = true
+readme.workspace       = true
+keywords.workspace     = true
+categories.workspace   = true
+
+# Deliberately empty: this crate is std-only by contract (ADR-0029 §2).
+# No serde, no griff-core, no time types — serialization and musical meaning
+# live in griff-swang and the frontends.
+[dependencies]
+
+[dev-dependencies]
+proptest = { workspace = true }
+
+[lints]
+workspace = true

pattern/proptest-regressions/lib.txt

@@ -0,0 +1,8 @@
+# Seeds for failure cases proptest has generated in the past. It is
+# automatically read and these particular cases re-run before any
+# novel cases are generated.
+#
+# It is recommended to check this file in to source control so that
+# everyone who runs the test benefits from these saved cases.
+cc 975a4af0b66d5bc280058fe9e6c7f192816380e212a17c8e32537190aad9940a # shrinks to rows = ["."]
+cc d13b8e3f8aba50341518bb0ff7f35717169e6da72df7093017acd585b05f4325 # shrinks to rows = ["."], depth = 0