* Sake: the changelog of 0.2.0, the first release meant for use

Everything the unreleased section had gathered becomes 0.2.0, grouped by
server, authorization, client, and testing and operations, with the
security fixes made before the release in a section of their own. 0.1.0
was an early preview, published but never announced: its entry says so.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RmGiJYwbdxJUjtQsHXHuxG

* Sake: README, guides and docs brought up to date for 0.2.0

The README installs ~> 0.2, says which Elixir and OTP Sake needs and
which dependencies are optional, lists every guide (the clustering one
was missing), several nodes and the JSON library among the features,
and what the conformance baselines list, exactly. The guides lose what
went stale as features landed: a refused call is never streamed, a
request state binds its owner, a refresh asks the subject module again,
the client opens a legacy GET stream in listen/3 but answers no request
on it, and the client's response bound and JSON library are documented.
protocol_versions.md no longer names a hidden module, so mix docs builds
without warnings.

The docs group every public module (Sake, the specs, the default consent
page, Sake.Server.Session) and show the logo; the description names what
the package grew into. SECURITY.md says how to report a vulnerability,
through GitHub's private reporting, and ships with the package.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RmGiJYwbdxJUjtQsHXHuxG

* Sake: version 0.2.0

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RmGiJYwbdxJUjtQsHXHuxG

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Co-authored-by: Claude <noreply@anthropic.com>