docs(readme): convert README.adoc -> Markdown README.md (#34)

README must be real Markdown to render in GitHub community-health, the GitHub
profile, and external MCP directories (Glama) — AsciiDoc shows as raw markup
there. pandoc asciidoc->GFM, badges fixed to clickable, SPDX header kept as an
HTML comment, duplicate README.adoc removed.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: hyperpolymath

README.adoc

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+<!--
+SPDX-License-Identifier: CC-BY-SA-4.0
+SPDX-FileCopyrightText: 2025-2026 Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
+-->
+
+# What Is This?
+
+Futharkiser identifies array-parallel patterns in your code, extracts
+them, generates [Futhark](https://futhark-lang.org) programs, and
+compiles those programs to **GPU kernels** (OpenCL, CUDA, or multicore
+CPU) — all without requiring the user to know anything about GPU
+programming.
+
+[Futhark](https://futhark-lang.org) (by Troels Henriksen et al., DIKU
+Copenhagen) is a purely functional array language that compiles to
+highly optimised GPU code. It guarantees no data races and achieves
+near-hand-tuned performance on parallel array operations. Almost nobody
+knows it exists. Futharkiser democratises GPU computing by putting
+Futhark behind a simple manifest.
+
+# How It Works
+
+Annotate array operations in your code with `#[futharkise]` (or describe
+them in `futharkiser.toml`). Futharkiser then:
+
+1.  **Analyses** your source code for parallelisable array patterns
+
+2.  **Extracts** operations that map to Futhark’s second-order array
+    combinators (SOACs): `map`, `reduce`, `scan`, `scatter`,
+    `flatten`/`unflatten`
+
+3.  **Proves** parallelism safety via the Idris2 ABI layer (no data
+    races, correct memory layouts, valid GPU buffer descriptors)
+
+4.  **Generates** Futhark programs with optimal data layouts and memory
+    transfers
+
+5.  **Compiles** via `futhark` `opencl`, `futhark` `cuda`, `futhark`
+    `multicore`, or `futhark` `c` (sequential, for debugging)
+
+6.  **Creates** a Zig FFI bridge so the compiled GPU kernels are
+    callable from your application with zero ceremony
+
+# Key Value
+
+- **GPU computing for everyone** — no CUDA/OpenCL expertise needed
+
+- **10-1000x speedups** on array-heavy workloads, with Futhark’s
+  compiler performing fusion, tiling, and memory coalescing
+  automatically
+
+- **Automatic memory management** across the CPU/GPU boundary
+  (host/device/shared memory spaces are tracked by the ABI layer)
+
+- **Safety guarantees** — Futhark is purely functional with no data
+  races; Idris2 proofs verify the interface contracts at compile time
+
+- **Multiple GPU backends** — OpenCL (widest hardware support), CUDA
+  (NVIDIA), multicore CPU (no GPU required), sequential C (debugging)
+
+# Use Cases
+
+- **Scientific computing** — matrix operations, PDE solvers, linear
+  algebra
+
+- **Image processing** — convolutions, filters, histograms on pixel
+  arrays
+
+- **Monte Carlo simulation** — massively parallel random sampling
+
+- **Neural network primitives** — custom forward/backward passes on
+  tensors
+
+- **Financial modelling** — option pricing, risk calculations over large
+  portfolios
+
+- **Signal processing** — FFT, spectral analysis on array data
+
+# Architecture
+
+Follows the hyperpolymath -iser pattern:
+
+    futharkiser.toml           User describes WHAT they want
+            |
+            v
+      Source Analysis           Identifies map/reduce/scan/scatter patterns
+            |
+            v
+      Idris2 ABI Layer          Proves parallelism safety, validates GPU buffer layouts
+      (src/interface/abi/)      Types: SOAC, GPUBackend, ArrayShape, ParallelPattern, MemorySpace
+            |
+            v
+      Futhark Codegen           Generates .fut programs with SOACs
+      (src/codegen/)
+            |
+            v
+      GPU Compilation           futhark opencl | futhark cuda | futhark multicore | futhark c
+            |
+            v
+      Zig FFI Bridge            C-ABI callable GPU kernels
+      (src/interface/ffi/)
+            |
+            v
+      Your Application          Calls GPU kernels as normal functions
+
+## Futhark SOACs (Second-Order Array Combinators)
+
+Futharkiser maps source patterns to these Futhark primitives:
+
+| SOAC | Description | Example pattern |
+|----|----|----|
+| `map` | Apply function to every element | `items.iter().map(|x|` `x` `*` `2)` |
+| `reduce` | Fold array with associative operator | `items.iter().sum()` |
+| `scan` | Inclusive prefix scan | Running totals, prefix sums |
+| `scatter` | Irregular write to array positions | Histogram binning, sparse updates |
+| `flatten`/`unflatten` | Reshape nested arrays | Matrix operations, batch processing |
+
+## GPU Backends
+
+| Backend | Use case | Flag |
+|----|----|----|
+| OpenCL | Widest hardware support (AMD, Intel, NVIDIA) | `--backend` `opencl` |
+| CUDA | NVIDIA GPUs (best NVIDIA performance) | `--backend` `cuda` |
+| Multicore CPU | No GPU available; still parallel | `--backend` `multicore` |
+| Sequential C | Debugging, correctness testing | `--backend` `c` |
+
+Part of the [-iser family](https://github.com/hyperpolymath/iseriser) of
+acceleration frameworks.
+
+# Status
+
+**Codebase in progress.** Architecture defined, CLI scaffolded, RSR
+template complete, Idris2 ABI types stubbed. Futhark codegen and GPU
+compilation pipeline are the next milestones.
+
+# Quick Start
+
+```bash
+# Initialise a manifest in your project
+futharkiser init
+
+# Edit futharkiser.toml to describe your array operations
+# Then generate, build, and run:
+futharkiser generate
+futharkiser build --backend opencl
+futharkiser run
+```
+
+# Building from Source
+
+```bash
+cargo build --release
+```
+
+# License
+
+SPDX-License-Identifier: CC-BY-SA-4.0