* feat(examples): add a reference host so an integration has something to copy

SharedOS leaves storage, durable stores, and the model to the host, and the
guide describes those ports without showing one. The first thing every
integration writes is therefore also the thing most likely to be wrong, and
two of its failure modes are silent.

`examples/reference-host` is a working host: a filesystem `files` provider
covering all twelve actions, SQLite stores for bounded uses, revocation,
namespace settings and audit, and an `AgentTurnDriver` over a live model.

Path safety is the part the kernel cannot help with. Authorization is decided
on the logical path but the provider serves the physical target, so staying
under the tenant root is not enough — a link that stays inside the tenant and
points at another subtree voids the grant without SharedOS seeing it. The
example plants that link and prints the outcome next to an in-scope read that
must still succeed, because a defence that only ever reports "blocked" proves
nothing.

Also record released changes in a changelog, and stop describing the
repository as private-source now that it is public.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* chore(release): v0.1.0-alpha.2

`deriveGrant` and the chain resolver landed after alpha.1 was tagged, so the
delegation model the README and the fleet example describe is not in any
published package. Anyone installing from npm and following the docs hits a
missing export.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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Co-authored-by: Claude Opus 5 <noreply@anthropic.com>