chore(service-disco): rename startDiscovering to registerInterest

[rlve]

Summary

Renames service-discovery calls to match vacp2p/nim-libp2p#2441, and bumps the flake to current nim-libp2p master.

• discoStartDiscovering → discoRegisterInterest
• discoStopDiscovering → discoUnregisterInterest
• C symbols and log strings updated to match.

Mix disabled

vacp2p/nim-libp2p#2378 moved mix out of nim-libp2p. The cbind layer no longer exports libp2p_mix_* / mount_mix / Libp2pMixReadBehavior / libp2p_curve25519_key_t etc.

Mix code has been disabled, with the assumption that it should stay in this module and can be easily brought back once a new cbind is available.

[Copilot]

Pull request overview

This PR aligns the module’s service-discovery API naming with upstream nim-libp2p changes (register/unregister “interest” vs start/stop “discovering”), bumps the pinned nim-libp2p revision in the Nix flake, and temporarily disables Mix-related code paths due to missing C bindings.

Changes:

• Renamed service discovery methods and underlying C symbol calls: *StartDiscovering/*StopDiscovering → *RegisterInterest/*UnregisterInterest.
• Disabled Mix compilation/tests via CMake source list changes and #if 0 guards.
• Updated flake.lock to track a newer nim-libp2p revision.

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
CMakeLists.txt	Stops building src/mix.cpp in the main module.
src/plugin.cpp	Disables mount_mix configuration wiring behind #if 0.
src/plugin.h	Hides Mix options/APIs behind #if 0; renames service discovery API declarations.
src/service_discovery.cpp	Renames service discovery implementation and switches to new C symbols.
examples/service_discovery.cpp	Updates example to call discoRegisterInterest/discoUnregisterInterest.
tests/CMakeLists.txt	Removes Mix sources/tests from the integration test build.
tests/integration_service_discovery.cpp	Updates tests to use discoRegisterInterest.
tests/sync.cpp	Disables Mix sync tests via #if 0 block.
flake.lock	Bumps the locked nim-libp2p input revision/hash.

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[Copilot]

Pull request overview

Copilot reviewed 9 out of 10 changed files in this pull request and generated 4 comments.