docs: correct opt-in build notes for kafka and mithril

[scarmuega]

Follow-up to #944 fixing two inaccurate notes about the opt-in (source-build) integrations. Docs/comments only — no behaviour change.

• mithril — Slim dependencies and ship a batteries-included default binary #944 said it's "unsupported on Windows MSVC". The green cargo check --all-features Windows CI check disproves that: mithril's GMP/blst C-crypto crates build and statically link on windows-msvc. It's opt-in because it's a heavy C toolchain (larger binary, much longer build), not for portability.
• kafka — now that the kafka feature pulls a vendored OpenSSL build, opt-in builds need a C compiler + Perl, not the platform's system OpenSSL dev libraries.
• Also reworded the zeromq note to make the real reason explicit: it dynamically links a system libzmq at runtime, so it can't ship in a portable prebuilt binary.

Touches the [package.metadata.dist] comment in Cargo.toml and the two installation docs.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Documentation
  • Clarified which integrations (Kafka, ZeroMQ, Mithril) are excluded from portable binary releases and their system/C dependency constraints.
  • Updated build prerequisites documentation with improved explanations of required toolchains and dependencies for building from source.

[coderabbitai]

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Review failed

Pull request was closed or merged during review

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: c12d7838-5a06-4677-a926-2b615db46ea3

📥 Commits

Reviewing files that changed from the base of the PR and between fa0a3b6 and 57837e3.

📒 Files selected for processing (3)

• Cargo.toml
• docs/v2/installation/binary_release.mdx
• docs/v2/installation/from_source.mdx

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📝 Walkthrough

Walkthrough

Comments in Cargo.toml and two installation documentation files (binary_release.mdx, from_source.mdx) are updated to clarify why kafka, zeromq, and mithril are excluded from the default portable binary, citing OpenSSL/C compiler requirements, dynamic libzmq linking, and the heavy GMP/blst crypto toolchain respectively. No code, dependency versions, or feature lists are changed.

Changes

Feature exclusion rationale clarification

Layer / File(s)

Summary

Feature exclusion comments and installation docs Cargo.toml, docs/v2/installation/binary_release.mdx, docs/v2/installation/from_source.mdx

Comment block in Cargo.toml reworded to "kept OUT (available via a source build) to keep the release lean and free of system/C dependencies." binary_release.mdx rewrites per-integration exclusion reasons. from_source.mdx updates the prerequisites table (kafka → vendored OpenSSL + C compiler + Perl; mithril → heavy GMP/blst C-crypto toolchain, slow builds) and the --all-features note to mention system libzmq and the mithril C-crypto toolchain.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Suggested reviewers

• paulobressan

Poem

🐇 Hop hop, the comments are clear,
No C deps shall cause the binary fear!
kafka, zeromq, mithril aside,
In source builds only they shall reside.
The lean release hops free with pride! 🌿

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: correcting documentation for opt-in build notes for kafka and mithril.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch docs/accurate-optin-build-notes

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