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.

tests/test_cli.py

@@ -1,4 +1,4 @@
-"""Tests for the freeroute CLI (Specctra DSN in, SES out).
+"""Tests for the rpmroute CLI (Specctra DSN in, SES out).
 
 Covers the engine selection contract: every engine must route a fixture from the
 command line, and every option the selected engine does not implement must fail
@@ -11,7 +11,7 @@ from pathlib import Path
 
 import pytest
 
-from freeroute.cli import ENGINE_OPTIONS, main
+from rpmroute.cli import ENGINE_OPTIONS, main
 
 FIXTURES = Path(__file__).parent / "dsn" / "fixtures"
 FIXTURE = FIXTURES / "simple_2net.dsn"