v0.21.0 — sliced delegation

v0.21.0 — sliced delegation

Architect-authored, test-gated vertical slices on the delegation pipeline: each
slice runs fresh/no-context in an isolated worktree gated by its own verification;
a deterministic wayfinder routes advance/repair/halt from objective gate results;
review and the advisor judge the composed candidate over the whole slice branch.
A mid-run halt after at least one slice advances yields a human-acceptable partial
candidate.

MCP wire PROTOCOL_VERSION 1.2.0 -> 1.3.0 (additive: slices, haltedSliceIndex).

Includes the crash-recovery reconciliation of the checkout-lease and quarantine/
in-lock-recheck models, and skips two POSIX-only lock-semantics tests on Windows.