Scaffold freeroute: Python port of the FreeRouting engine

Pure-Python PCB autorouter replacing the freerouting.jar step in kicad-mcp.
Contract is Specctra DSN in, SES out — a drop-in for the JAR so the toolchain
needs no JVM. Includes pyproject (uv/ruff/pytest, src-layout) and a porting
plan seeded for study of the upstream FreeRouting Java source.

README.md

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+# freeroute
+
+A native Python PCB autorouter — a Java-free port of the
+[FreeRouting](https://github.com/freerouting/freerouting) engine.
+
+## Why
+
+`kicad-mcp` currently autoroutes by shelling out to `freerouting.jar`, which
+drags in a JVM dependency. `freeroute` reimplements the routing engine in
+pure Python so the toolchain needs no Java at all.
+
+## The contract
+
+The entire integration surface is two Specctra files:
+
+```
+board.dsn  ──▶  freeroute  ──▶  board.ses
+(unrouted)                       (routed session: traces + vias)
+```
+
+`kicad-cli` already exports `.dsn` and imports `.ses`, so `freeroute` is a
+drop-in replacement for the JAR step — nothing else in the pipeline changes.
+
+## Status
+
+Pre-alpha. Under active development. See [`docs/PORTING_PLAN.md`](docs/PORTING_PLAN.md)
+for the architecture and porting roadmap.
+
+## Usage (target)
+
+```bash
+freeroute board.dsn -o board.ses
+```
+
+## Development
+
+```bash
+uv sync
+uv run pytest
+uv run ruff check src/ tests/
+```
+
+## License
+
+GPL-3.0-or-later, matching the FreeRouting source it is ported from.