docs: update README with accurate features and add roadmap

Remove NFP pair fitting claim from features (not yet integrated).
Qualify lead-in/lead-out as engine-only (UI coming soon).
Mark --autonest CLI option as experimental. Add Roadmap section
with planned work: NFP nesting, lead-in UI, sheet cut-offs,
post-processors, and shape library UI.

Add documentation maintenance instruction to CLAUDE.md requiring
README.md and CLAUDE.md updates when project structure changes.

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

CLAUDE.md

@@ -37,16 +37,15 @@ Nesting algorithms with a pluggable engine architecture. `NestEngineBase` is the
 
 - **Engine hierarchy**: `NestEngineBase` (abstract) → `DefaultNestEngine` (Linear, Pairs, RectBestFit, Remainder phases). Custom engines subclass `NestEngineBase` and register via `NestEngineRegistry.Register()` or as plugin DLLs in `Engines/`.
 - **NestEngineRegistry**: Static registry — `Create(Plate)` factory, `ActiveEngineName` global selection, `LoadPlugins(directory)` for DLL discovery. All callsites use `NestEngineRegistry.Create(plate)` except `BruteForceRunner` which uses `new DefaultNestEngine(plate)` directly for training consistency.
-- **BestFit/**: NFP-based pair evaluation pipeline — `BestFitFinder` orchestrates angle sweeps, `PairEvaluator`/`IPairEvaluator` scores part pairs, `RotationSlideStrategy`/`ISlideComputer` computes slide distances. `BestFitCache` and `BestFitFilter` optimize repeated lookups.
-- **RectanglePacking/**: `FillBestFit` (single-item fill, tries horizontal and vertical orientations), `PackBottomLeft` (multi-item bin packing, sorts by area descending). Both operate on `Bin`/`Item` abstractions.
-- **CirclePacking/**: Alternative packing for circular parts.
-- **ML/**: `AnglePredictor` (ONNX model for predicting good rotation angles), `FeatureExtractor` (part geometry features), `BruteForceRunner` (full angle sweep for training data).
-- `FillLinear`: Grid-based fill with directional sliding.
-- `Compactor`: Post-fill gravity compaction — pushes parts toward a plate edge to close gaps.
-- `FillScore`: Lexicographic comparison struct for fill results (count > utilization > compactness).
+- **Fill/** (`namespace OpenNest.Engine.Fill`): Fill algorithms — `FillLinear` (grid-based), `FillExtents` (extents-based pair tiling), `PairFiller` (interlocking pairs), `ShrinkFiller`, `RemnantFiller`/`RemnantFinder`, `Compactor` (post-fill gravity compaction), `FillScore` (lexicographic comparison: count > utilization > compactness), `Pattern`/`PatternTiler`, `PartBoundary`, `RotationAnalysis`, `AngleCandidateBuilder`, `BestCombination`, `AccumulatingProgress`.
+- **Strategies/** (`namespace OpenNest.Engine.Strategies`): Pluggable fill strategy layer — `IFillStrategy` interface, `FillContext`, `FillStrategyRegistry` (auto-discovers strategies via reflection, supports plugin DLLs), `FillHelpers`. Built-in strategies: `LinearFillStrategy`, `PairsFillStrategy`, `RectBestFitStrategy`, `ExtentsFillStrategy`.
+- **BestFit/** (`namespace OpenNest.Engine.BestFit`): NFP-based pair evaluation pipeline — `BestFitFinder` orchestrates angle sweeps, `PairEvaluator`/`IPairEvaluator` scores part pairs, `RotationSlideStrategy`/`ISlideComputer` computes slide distances. `BestFitCache` and `BestFitFilter` optimize repeated lookups.
+- **RectanglePacking/** (`namespace OpenNest.RectanglePacking`): `FillBestFit` (single-item fill, tries horizontal and vertical orientations), `PackBottomLeft` (multi-item bin packing, sorts by area descending). Both operate on `Bin`/`Item` abstractions.
+- **CirclePacking/** (`namespace OpenNest.CirclePacking`): Alternative packing for circular parts.
+- **Nfp/** (`namespace OpenNest.Engine.Nfp`): NFP-based nesting (not yet integrated) — `AutoNester` (mixed-part nesting with simulated annealing), `BottomLeftFill` (BLF placement), `NfpCache` (computed NFP caching), `SimulatedAnnealing` (optimizer), `INestOptimizer`/`NestResult`.
+- **ML/** (`namespace OpenNest.Engine.ML`): `AnglePredictor` (ONNX model for predicting good rotation angles), `FeatureExtractor` (part geometry features), `BruteForceRunner` (full angle sweep for training data).
 - `NestItem`: Input to the engine — wraps a `Drawing` with quantity, priority, and rotation constraints.
 - `NestProgress`: Progress reporting model with `NestPhase` enum for UI feedback.
-- `RotationAnalysis`: Analyzes part geometry to determine valid rotation angles.
 
 ### OpenNest.IO (class library, depends on Core)
 File I/O and format conversion. Uses ACadSharp for DXF/DWG support.
@@ -99,9 +98,14 @@ Always use Roslyn Bridge MCP tools (`mcp__RoslynBridge__*`) as the primary metho
 
 - Always use `var` instead of explicit types (e.g., `var parts = new List<Part>();` not `List<Part> parts = new List<Part>();`).
 
+## Documentation Maintenance
+
+Always keep `README.md` and `CLAUDE.md` up to date when making changes that affect project structure, architecture, build instructions, dependencies, or key patterns. If you add a new project, change a namespace, modify the build process, or alter significant behavior, update both files as part of the same change.
+
 ## Key Patterns
 
 - OpenNest.Core uses multiple namespaces: `OpenNest` (root domain), `OpenNest.CNC`, `OpenNest.Geometry`, `OpenNest.Converters`, `OpenNest.Math`, `OpenNest.Collections`.
+- OpenNest.Engine uses sub-namespaces: `OpenNest.Engine.Fill` (fill algorithms), `OpenNest.Engine.Strategies` (pluggable strategy layer), `OpenNest.Engine.BestFit`, `OpenNest.Engine.Nfp` (NFP-based nesting, not yet integrated), `OpenNest.Engine.ML`, `OpenNest.Engine.RapidPlanning`, `OpenNest.Engine.Sequencing`.
 - `ObservableList<T>` provides ItemAdded/ItemRemoved/ItemChanged events used for automatic quantity tracking between plates and drawings.
 - Angles throughout the codebase are in **radians** (use `Angle.ToRadians()`/`Angle.ToDegrees()` for conversion).
 - `Tolerance.Epsilon` is used for floating-point comparisons across geometry operations.

README.md

@@ -9,14 +9,14 @@ OpenNest takes your part drawings, lets you define your sheet (plate) sizes, and
 ## Features
 
 - **DXF Import/Export** — Load part drawings from DXF files and export completed nest layouts
-- **Multiple Fill Strategies** — Grid-based linear fill, NFP (No Fit Polygon) pair fitting, and rectangle bin packing
+- **Multiple Fill Strategies** — Grid-based linear fill and rectangle bin packing
 - **Part Rotation** — Automatically tries different rotation angles to find better fits
 - **Gravity Compaction** — After placing parts, pushes them together to close gaps
 - **Multi-Plate Support** — Work with multiple plates of different sizes and materials in a single nest
 - **G-code Output** — Post-process nested layouts to G-code for CNC cutting machines
 - **Built-in Shapes** — Create basic geometric parts (circles, rectangles, triangles, etc.) without needing a DXF file
 - **Interactive Editing** — Zoom, pan, select, clone, and manually arrange parts on the plate view
-- **Lead-in/Lead-out & Tabs** — Configure cutting parameters like approach paths and holding tabs
+- **Lead-in/Lead-out & Tabs** — Cutting parameters like approach paths and holding tabs (engine support, UI coming soon)
 
 ![OpenNest - 44 parts nested on a 60x120 plate](screenshots/screenshot-nest-2.png)
 
@@ -67,7 +67,7 @@ dotnet run --project OpenNest.Console/OpenNest.Console.csproj -- <input-files> [
 # Import a DXF and fill a 60x120 plate
 dotnet run --project OpenNest.Console/OpenNest.Console.csproj -- part.dxf --size 60x120
 
-# Import multiple DXFs with NFP-based auto-nesting
+# Import multiple DXFs with mixed-part auto-nesting (experimental)
 dotnet run --project OpenNest.Console/OpenNest.Console.csproj -- part1.dxf part2.dxf --size 60x120 --autonest
 ```
 
@@ -86,7 +86,7 @@ dotnet run --project OpenNest.Console/OpenNest.Console.csproj -- project.zip ext
 | Option | Description |
 |--------|-------------|
 | `--size <WxL>` | Plate size (e.g. `60x120`). Required for DXF-only mode. |
-| `--autonest` | Use NFP-based mixed-part nesting instead of linear fill |
+| `--autonest` | Use mixed-part nesting instead of linear fill (experimental) |
 | `--drawing <name>` | Select which drawing to fill with (default: first) |
 | `--quantity <n>` | Max parts to place (default: unlimited) |
 | `--spacing <value>` | Override part spacing |
@@ -146,6 +146,14 @@ For most users, only these matter:
 | DWG (AutoCAD Drawing) | Yes | No |
 | G-code | No | Yes (via post-processors) |
 
+## Roadmap
+
+- **NFP-based nesting** — No Fit Polygon algorithms and simulated annealing optimizer exist in the engine but aren't integrated into the UI or engine registry yet
+- **Lead-in/Lead-out UI** — Engine support for lead-ins, lead-outs, and tabs is implemented; needs a UI for configuration
+- **Sheet cut-offs** — Cut the sheet to size after nesting to reduce waste
+- **Post-processors** — Plugin interface (`IPostProcessor`) is in place; need to ship built-in post-processors for common CNC controllers
+- **Shape library UI** — Built-in shape generation code exists; needs a browsable library UI for quick access
+
 ## Status
 
 OpenNest is under active development. The core nesting workflows function, but there's plenty of room for improvement in packing efficiency, UI polish, and format support. Contributions and feedback are welcome.