Open a mind fail-closed over an owned redb store

Cut 8, Huginn half, commit 1 of 4: the store port, the opener and the
identity rules. `huginn-mind` gains its dependencies (`cultcache-rs` at
Epiphany's pin `a0813c6`, `epiphany-pipeline` at `a65c6420`, the Epiphany
half of this cut), `store.rs` with the one narrow `MindStore` trait that
injects compare-and-swap, `mind.rs` with `Mind::open` and `open_with`, and
`refusal.rs` with the organ's refusal vocabulary.

The opener refuses in order and attaches nothing until every gate passes:
a foreign type, a foreign epoch, a missing identity, an identity naming
another instance. The path under the state root is derived from the slug;
the `instance` document is the authority, so a store copied into another
instance's directory is refused. The owned store's exclusive lock is the
single-writer mechanism: a second `Mind::open` of the same path is
`MindAlreadyOwned`.

The receipt type and the two provenance shapes (`Faculty`,
`PipelineProvenance`) land here rather than in the later commits because
the opener registers the receipt's type id, and their only consumer is the
receipt; the commit primitive itself is the next commit. `MindRefusal`
carries a serde remote definition of the leaf's `PipelineRefusal`, which
derives neither `Serialize` nor `JsonSchema` at the pinned rev; it is
compiled against the leaf's type so a leaf change breaks the build rather
than drifting.

`Cargo.lock` is regenerated and gains 90 packages. The map predicted a
CRLF-to-LF rewrite of the whole file; the file was already LF in the index
and stays LF, so the diff is additions only.

README and AGENTS now say `huginn-mind` is live and the other two crates
are stubs.

Builds: `cargo check -p huginn-mind --lib --tests` and `cargo test -p
huginn-mind --lib` (4 tests) pass. This commit carries dead-code warnings
on the store and cache accessors and the refusing test store; commits 2 and
3 consume them.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

AGENTS.md

@@ -13,10 +13,10 @@ Studio's job, not Huginn's.
 - Upstream: `https://github.com/GameCult/Huginn.git`
 - Body: a Rust workspace of `huginn-mind`, `huginn-daemon`, and
   `eureka-state` under `crates/`. Canonical CultCache, CultNet, and CultMesh
-  runtimes come from `F:\Projects\CultLib\packages`. The crates are stubs
-  with no dependencies; each named cut of the Eureka pipeline-state campaign
-  fills one in. Until then nothing here persists, admits, publishes, or
-  connects.
+  runtimes come from `F:\Projects\CultLib\packages`. `huginn-mind` is live:
+  it persists and admits an instance's mind, over `cultcache-rs` and
+  `epiphany-pipeline` pinned by git rev. `huginn-daemon` and `eureka-state`
+  are stubs with no dependencies; nothing here publishes or connects yet.
 - Owned: an instance's memory documents, their admission, and their CultNet
   publication.
 - Depends on: Qdrant, directly. Unreachable Qdrant is a loud refusal, never a