Barbacane v0.8.1

Patch release: fixes a regression that made the barbacane-standalone image unable to serve specs under 0.8's capability enforcement.

Fixed

• plugins: WASM plugins are now self-describing. The SDK macros (#[barbacane_middleware] / #[barbacane_dispatcher]) embed each plugin's plugin.toml into a custom wasm section (barbacane_manifest), and the compiler reads declared capabilities directly from the binary (falling back to a sibling/downloaded plugin.toml for plugins built before 0.8.1). The standalone image shipped plugins as bare .wasm files with no sidecar plugin.toml, so every bundled plugin was compiled with empty capabilities and the data plane rejected the first one to import a host function under capabilities_enforced (plugin '<name>' violates its declared capabilities: plugin imports undeclared host function: ...). As a result the standalone image could compile a spec but not serve it. Capability contracts now travel inside the .wasm, so no sidecar file has to accompany a plugin. A compile-time warning is emitted when a plugin resolves with no manifest from either source.