Define PFFTT for use in running Technique documents

[istathar]

We define the Procedure interchange Format For Transferring Techniques, PFFTT, done in the same modified BNF style as the one for the Technique language.

[istathar]

The working example used while formalizing this description was:

2026-05-16T12:50:30Z 015003 / Start file:///home/andrew/src/technique-lang/technique/examples/prototype/NetworkProbe.tq
2026-05-16T12:50:32Z 015003 /local_network:1 Begin
2026-05-16T12:50:42Z 015003 /local_network:1 Execute exec()
2026-05-16T12:50:48Z 015003 /local_network:1 Done ()
2026-05-17T00:28:25Z 015003 / Resume
2026-05-17T00:28:26Z 015003 /local_network:2 Begin
2026-05-17T00:28:30Z 015003 /local_network:2 Skip
2026-05-17T00:28:32Z 015003 /local_network:3 Begin
2026-05-17T00:29:15Z 015003 /local_network:3 Done [ address = "192.168.1.1", latency = 355 ms ]
2026-05-17T00:29:20Z 015003 /local_network:4 Begin
2026-05-17T00:30:00Z 015003 /local_network:4 Done ()
2026-05-17T00:30:05Z 015003 /local_network:5 Begin
2026-05-17T00:31:30Z 015003 /local_network:5 Invoke probe_border_router:
2026-05-17T00:31:31Z 015003 /probe_border_router:1 Begin
2026-05-17T00:32:01Z 015003 /probe_border_router:1 Done ()
2026-05-17T00:32:02Z 015003 /probe_border_router:2/a/-1 Begin
2026-05-17T00:32:05Z 015003 /probe_border_router:2/a/-1 Done ()