feat(coven): consume strict runtime policy admission contract

[BunsDev]

Authorized cross-repository delivery

Tracks the SDK side of OpenCoven/wand#9 and OpenCoven/wand#10. BunsDev explicitly authorized cross-repository implementation and delegated contract design decisions to Cody on September 10, 2026.

The canonical policy and enforcement decisions belong in Coven Rust. SDK types and fixtures must follow the resulting reviewed version, not invent a competing authority contract.

Required outcome

• Add a strict opt-in typed consumer for the canonical Coven session-policy contract without changing existing health-only client semantics.
• Preserve import purity, bounded transport responses, explicit unsupported behavior and safe error metadata.
• Keep availability/identity/metadata distinct from actual authority. No empty or unknown grant input becomes unlimited authority; no restricted request silently falls back to legacy.
• Bind and validate the exact accepted request and lifecycle evidence using shared canonical fixtures.
• Reuse contract provenance/import conventions and intentional API baseline updates; include focused tests, docs and a Changeset for public behavior.
• Maintain server-side authority ownership; the SDK cannot manufacture enforcement evidence or rely on prompt text.

Starting source: SDK d1c9ddf2a7514e56fac26e20d571114ca97fe623; isolated branch feat/wand-runtime-policy. The separate dirty Cave continuity/chapter worktree is out of scope.

No hosted workflows, live user daemon/harness runs, credential lookup or provider actions are authorized by this issue. Publication must respect actual workflow triggers; do not disable automation or weaken gates as a workaround.

[BunsDev]

Canonical server ownership is OpenCoven/coven#990. The initial coven.session-policy.v1 consumer must recognize only strict discovery and correlated refusal; it cannot manufacture accepted grants. Preserve health-only transport semantics and provide a separate constrained opt-in Unix policy transport, using the existing peer/socket validation and explicit fixed endpoints. No default discovery, credentials or network effects at import time. Shared golden fixtures and exact transmitted-body SHA256 are the integration gate; positive effect enforcement remains unavailable.

[BunsDev]

Implementation and fixture blockers are cleared. Published feat/wand-runtime-policy at 4a02eec. Supported @opencoven/coven-client root exports include the strict refusal client and separately opt-in real Unix transport with fixed discovery GET/restricted POST, native peer/path validation, exact immutable octets, bounded framing, cancellation/deadlines and no retry/fallback.

All four golden fixtures match producer OpenCoven/coven commit 8ae022a70ce2506e0e3b4345b8e567fe94380ce5 byte-for-byte, with packaged provenance. Public API baselines and Changeset are synchronized. Evidence:450 targeted regressions, type/lint/build/packed-surface coverage; parent reran176 focused tests and reviewed compatibility-sensitive framing changes. Staged Gitleaks and existing secret/private-key hooks passed. Feature push produced no hosted run.

A reviewed native peer-identity provider remains mandatory for real Unix use; Windows policy transport is explicitly unsupported. This is refusal-only v1, not enforcement or a grant lifecycle. Existing package publication gates remain intact. No live daemon/provider or npm release was used. The feature branch is preserved; no PR was created under the standing no-hosted-workflow constraint.