chore: extract mix to logos-co/nim-libp2p-mix

[chaitanyaprem]

Summary

Mix has been extracted out of nim-libp2p into its own repository at
logos-co/nim-libp2p-mix
so it can evolve independently of the core libp2p library. This PR
removes the mix code from nim-libp2p.

What's removed

• Source: `libp2p/protocols/mix/` (tree) and `libp2p/protocols/mix.nim` (facade)
• Tests: `tests/libp2p/mix/`
• Example: `examples/mix_ping.nim`
• Peer store: `MixPubKeyBook` from `libp2p/peerstore.nim` (only used by mix)
• C bindings: 7 `libp2p_mix_*` exported procs, related types/fields, and request processors in `cbind/`
• Compile flag: `-d:libp2p_mix_experimental_exit_is_dest` from the default test cfg (the new repo sets it in its own nimble file)
• Docs: `docs/protocols_mix.md`, `docs/protocols_mix_spam_protection.md`, README & copilot-instructions entries

Net change: 49 files deleted, 16 modified (−538 / +6).

Consumer migrations (already up)

These should land before this PR merges, otherwise consumers break:

• `logos-co/mix-rln-spam-protection-plugin#6` — switch import to `libp2p_mix/spam_protection`
• `logos-messaging/logos-delivery#3842` — switch all waku imports, add `libp2p_mix` nimble dep, add new submodule

Verification

• `nim check` on `libp2p.nim` and `cbind/libp2p.nim` after deletion: clean ✓
• 5-node mixnet simulation in logos-delivery (chat2mix + lightpush) runs end-to-end with the new `libp2p_mix` package ✓

History preservation

Full mix git history is preserved in `logos-co/nim-libp2p-mix` with original
authors, dates, and PR references rewritten as cross-repo links to
`vacp2p/nim-libp2p#NNNN`.

Test plan

• CI green on this branch (full test suite + interop)
• Close LIONESS PR feat(mix): use LIONESS for Sphinx payload encryption #2349 with a pointer to logos-co/nim-libp2p-mix#mix-payload-lioness

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.41%. Comparing base (220a07f) to head (fbc38e9).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2378      +/-   ##
==========================================
- Coverage   74.06%   73.41%   -0.65%     
==========================================
  Files         170      149      -21     
  Lines       22357    20027    -2330     
  Branches       19       19              
==========================================
- Hits        16558    14703    -1855     
+ Misses       5799     5324     -475     

Files with missing lines	Coverage Δ
libp2p/peerstore.nim	94.89% <ø> (ø)

... and 3 files with indirect coverage changes

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[Copilot]

Pull request overview

This PR removes the Mix protocol implementation (and all related tests, docs, examples, peerstore book, build flags, and C bindings) from nim-libp2p, following the extraction of Mix into logos-co/nim-libp2p-mix so it can evolve independently of the core library.

Changes:

• Deleted the Mix protocol code under libp2p/protocols/mix/ and the libp2p/protocols/mix.nim facade.
• Removed Mix-specific tests/examples/docs and related references in repository docs and example runner.
• Removed Mix-related peerstore and C-bindings surface area, including config flags and exported Mix APIs.

Reviewed changes

Copilot reviewed 65 out of 65 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/libp2p/test_peer_store.nim	Removes MixPubKeyBook tests from the PeerStore suite.
tests/libp2p/mix/utils.nim	Deletes Mix test utilities (switch setup, helpers, fake protocols).
tests/libp2p/mix/test_tag_manager.nim	Deletes Mix replay-tag manager tests.
tests/libp2p/mix/test_sphinx.nim	Deletes Sphinx packet construction/processing tests.
tests/libp2p/mix/test_spam_protection_interface.nim	Deletes Mix spam-protection interface tests.
tests/libp2p/mix/test_serialization.nim	Deletes Mix serialization tests (Header/Message/SphinxPacket/SURBs).
tests/libp2p/mix/test_seq_no_generator.nim	Deletes Mix seq-no generator tests.
tests/libp2p/mix/test_pool.nim	Deletes Mix node pool tests.
tests/libp2p/mix/test_multiaddr.nim	Deletes Mix multiaddr serialization/conversion tests.
tests/libp2p/mix/test_mix_message.nim	Deletes MixMessage serialization/deserialization tests.
tests/libp2p/mix/test_fragmentation.nim	Deletes Mix payload fragmentation/padding tests.
tests/libp2p/mix/test_delay_strategy.nim	Deletes Mix delay strategy tests.
tests/libp2p/mix/test_curve25519.nim	Deletes Mix curve25519 helper tests.
tests/libp2p/mix/test_crypto.nim	Deletes Mix crypto helper tests (AES-CTR/SHA256/HMAC/KDF).
tests/libp2p/mix/test_cover_traffic.nim	Deletes Mix cover-traffic unit tests.
tests/libp2p/mix/spam_protection_impl.nim	Deletes spam-protection test implementations used by Mix tests.
tests/libp2p/mix/mock_mix.nim	Deletes MockMixProtocol used in integration tests.
tests/libp2p/mix/component/test_spam_protection.nim	Deletes Mix protocol spam-protection integration tests.
tests/libp2p/mix/component/test_security.nim	Deletes Mix protocol security integration tests (replay/failure behavior).
tests/libp2p/mix/component/test_node_failures.nim	Deletes Mix node-failure integration tests (multi-SURB, invalid nodes, etc.).
tests/libp2p/mix/component/test_message_delivery.nim	Deletes Mix message delivery integration tests (reply/no-reply, delays, concurrency).
tests/libp2p/mix/component/test_cover_traffic.nim	Deletes Mix cover-traffic integration tests.
tests/libp2p/mix/component/test_connection_api.nim	Deletes Mix connection API integration tests.
README.md	Removes Mix from the documented list of implemented protocols.
libp2p/protocols/mix/tag_manager.nim	Deletes Mix replay-tag manager implementation.
libp2p/protocols/mix/sphinx.nim	Deletes Sphinx packet construction/processing implementation used by Mix.
libp2p/protocols/mix/spam_protection.nim	Deletes Mix spam-protection interface and helpers.
libp2p/protocols/mix/serialization.nim	Deletes Mix header/message/SphinxPacket/SURB serialization code.
libp2p/protocols/mix/seqno_generator.nim	Deletes Mix sequence-number generation logic.
libp2p/protocols/mix/reply_connection.nim	Deletes Mix reply connection implementation.
libp2p/protocols/mix/pool.nim	Deletes Mix node pool abstraction backed by PeerStore.
libp2p/protocols/mix/multiaddr.nim	Deletes Mix-specific multiaddr encoding/decoding helpers.
libp2p/protocols/mix/mix_node.nim	Deletes Mix node identity/public-info structures and generators.
libp2p/protocols/mix/mix_metrics.nim	Deletes Mix metrics definitions.
libp2p/protocols/mix/mix_message.nim	Deletes MixMessage encoding/decoding logic.
libp2p/protocols/mix/fragmentation.nim	Deletes Mix message padding/chunking implementation.
libp2p/protocols/mix/exit_layer.nim	Deletes Mix exit-layer forwarding/handler logic.
libp2p/protocols/mix/exit_connection.nim	Deletes MixExitConnection implementation.
libp2p/protocols/mix/entry_connection.nim	Deletes MixEntryConnection and toConnection construction.
libp2p/protocols/mix/delay.nim	Deletes Mix Delay type and conversions.
libp2p/protocols/mix/delay_strategy.nim	Deletes Mix delay strategy implementations.
libp2p/protocols/mix/curve25519.nim	Deletes Mix curve25519 wrapper/utilities.
libp2p/protocols/mix/crypto.nim	Deletes Mix crypto helpers (AES-CTR/HMAC/KDF/SHA256).
libp2p/protocols/mix/benchmark.nim	Deletes Mix benchmarking metadata/logging helper.
libp2p/protocols/mix.nim	Deletes the Mix protocol facade/re-exports and helper read behaviors.
libp2p/peerstore.nim	Removes the MixPubKeyBook type and the curve25519 dependency only used by Mix.
libp2p.nimble	Removes the default test compile flag for experimental Mix behavior.
examples/mix_ping.nim	Deletes the Mix ping example.
examples/examples_run.nim	Removes mix_ping from the runnable examples aggregation.
docs/README.md	Removes Mix docs links from the docs index.
docs/protocols_mix.md	Deletes Mix protocol documentation page.
docs/protocols_mix_spam_protection.md	Deletes Mix spam-protection documentation page.
docs/development.md	Removes nimble testpath mix from development/testing docs.
cbind/types.nim	Removes Mix fields/types from the C bindings LibP2P object.
cbind/libp2p.nim	Removes exported C APIs related to Mix (dialing, key helpers, node pool, etc.).
cbind/libp2p.h	Removes Mix C API declarations/types and config flag exposure.
cbind/libp2p_thread/inter_thread_communication/requests/libp2p_stream_requests.nim	Removes Mix stream request types/fields and request processors.
cbind/libp2p_thread/inter_thread_communication/requests/libp2p_lifecycle_requests.nim	Removes Mix protocol mounting/config plumbing.
cbind/libp2p_thread/inter_thread_communication/libp2p_thread_request.nim	Removes Mix request dispatch cases from the thread request processor.
cbind/ffi_types.nim	Removes Mix-related FFI config fields and key/read-behavior types.
cbind/examples/mix.c	Deletes the Mix C-bindings example.
cbind/cbind.nimble	Stops building/running the removed Mix C example in the cbind examples task.
.github/copilot-instructions.md	Removes Mix-specific repo layout/docs/flags references from contributor instructions.

[richard-ramos]

FYI @gmelodie , merging this will require changes in logos libp2p module

[Copilot]

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