Rename to rpmroute

The router began as a port of FreeRouting and has grown its own engine
(negotiated congestion, tree nets, exact checks, axis escapes), and
'freeroute' was one letter from the project it no longer follows. The
package, module and command are now rpmroute; the freeroute command stays
as an alias, and the RPMROUTE / RPMROUTE_ORACLE_JAVA variables fall back
to the old FREEROUTE names. Version 2026.10.07. Routing is unchanged: a
PCBench board routes to a byte-identical session either way.

docs/PORTING_PLAN.md

@@ -43,7 +43,7 @@ the output. Match that I/O and the rest of `kicad-mcp` is unchanged.
 4. **Autorouter core** — maze routing with rip-up-and-retry. Start grid-based
    Manhattan/45° for an MVP; converge toward FreeRouting's approach. _(TBD.)_
 5. **Optimize pass** — via minimization, trace smoothing. _(TBD.)_
-6. **CLI + kicad-mcp integration** — `freeroute board.dsn -o board.ses`, then
+6. **CLI + kicad-mcp integration** — `rpmroute board.dsn -o board.ses`, then
    swap it in behind `kicad_mcp/utils/freerouting_engine.py`'s JAR step.
 
 ## Validation strategy