docs: add TOPOLOGY.md

Document purpose, module structure, and data flow for this -iser tool.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: hyperpolymath

TOPOLOGY.md

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+<!-- SPDX-License-Identifier: PMPL-1.0-or-later -->
+<!-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk> -->
+# TOPOLOGY.md — chapeliser
+
+## Purpose
+
+chapeliser is a general-purpose Chapel acceleration framework that distributes any workload across Chapel clusters without the user writing Chapel code. It reads a `chapeliser.toml` manifest describing entry points, data partition strategies, and gather strategies, then generates Chapel wrapper code, a Zig FFI bridge, and C headers. chapeliser is priority #2 in the -iser family, targeting any compute workload that benefits from data-parallel or distributed execution.
+
+## Module Map
+
+```
+chapeliser/
+├── src/
+│   ├── main.rs                    # CLI entry point (clap): init, validate, generate, build, run, info
+│   ├── lib.rs                     # Library API
+│   ├── manifest/mod.rs            # chapeliser.toml parser
+│   ├── codegen/mod.rs             # Chapel wrapper, Zig FFI bridge, C header generation
+│   └── ...                        # [WIP] partition/gather strategy modules
+├── examples/                      # Worked examples
+├── verification/                  # Proof harnesses
+├── container/                     # Stapeln container ecosystem
+└── .machine_readable/             # A2ML metadata
+```
+
+## Data Flow
+
+```
+chapeliser.toml manifest
+        │
+   ┌────▼────┐
+   │ Manifest │  parse + validate entry points, partition + gather strategies
+   │  Parser  │
+   └────┬────┘
+        │  validated acceleration config
+   ┌────▼────┐
+   │ Analyser │  inspect source entry points, resolve types
+   └────┬────┘
+        │  intermediate representation
+   ┌────▼────┐
+   │ Codegen  │  emit generated/chapeliser/ (Chapel wrappers, Zig FFI, C headers)
+   └────┬────┘
+        │  Chapel + FFI artifacts
+   ┌────▼────┐
+   │  Chapel  │  compile + distribute across Chapel cluster
+   └─────────┘
+```