[Mouzayan]

Summary

Add runnable demo and pingnode commands using the existing TCP, Noise, and muxer stack. The demo runs ping, identify, and echo between two loopback hosts. The ping node serves until stdin EOF or authenticates a peer and pings once.

Closes #22.

What changed

• Add the pinned CLI parser and validate arguments before creating hosts, with single-line usage errors.
• Add command deadlines, stream cleanup, and shutdown of every owned host.
• Add echo test support, live CLI tests, and bidirectional Go ping checks.

Test plan

• Final-head Linux CI: lake build, lake test, and lake test -- +RTS -N1 -RTS. Both suites passed 28,107 checks, with zero failures and four documented skips.
• Import lint (190 modules), vector provenance, native hardening, and repository guards.
• Recorded live checks passed for the loopback demo and ping in both Go-to-Lean and Lean-to-Go directions.

Risk / trust footprint

Adds the pinned lean4-cli parser. The Go helper is test-only. No new axioms, sorry, partial definitions, native_decide, unsafe code, or FFI declarations.

Notes for reviewers

The unchanged local macOS Streams reset test still fails (Tests/Streams.lean:985). Required Linux gates pass.
Callback handling and cleanup order were checked by inspection; exit-status examples are kernel-checked. Direct callback fault injection is not covered.
Echo handles one chunk. W5.9 is separate. Contributor-selected decisions and detailed contracts are in the CLI architecture.

LICENSE (LGPL version 3)

• I have read and accepted LICENSE (LGPL version 3), NOTICE and CLA in the root of this project.