feat: bind Host interfaces to scope Object lifetimes

Register explicit scope/name coordinates independently of Definition type. Require provider-attested current scope snapshots for fetch and dispatch, compare optional scope_ref at membership precedence, and retain the same Descriptor through result validation.

Migrate FS pinned-root boundaries and public self-scope example; document provider atomicity/lifecycle and root-only FS support. Add lifecycle, ref, replacement-race, root-lineage and compile-time exposure regressions.

Validation: cargo fmt --all --check; git diff --check; cargo check --workspace --all-targets; cargo test --workspace --all-targets and --doc (232 passing test-harness cases including doctests); nix develop --command cargo clippy --workspace --all-targets -- -D warnings; RUSTDOCFLAGS=-Dwarnings cargo doc --workspace --no-deps. Narrow wip-host suite also passed.

CHANGELOG.md

@@ -8,8 +8,14 @@ All notable changes to the published WIP Rust crates are documented here.
   exact `(scope, name)` records in Objects, fetches and calls, with optional
   opaque `scope_ref` metadata. Adds shape and placement-aware scope validation
   without changing routes, validators or the wire error-code set.
-- Mechanically migrates workspace consumers and fixtures. See [MIGRATION.md](MIGRATION.md)
-  for API/wire examples and the deferred Host/Client lifecycle semantics.
+- Breaking Host registration migration to explicit Scope publication lifetimes and
+  local names, with coherent provider-attested scope Object binding for fetch and
+  dispatch. Supplied scope_ref is checked at membership precedence; scope deletion
+  retires retained tokens, while ordinary Object state updates preserve lifetime.
+- Migrates FS root publication and public-example self-scopes to the Host API,
+  including coherent backend observations and explicit built-in names. Non-root
+  FS semantics and Client cache recovery remain follow-up work. See
+  [MIGRATION.md](MIGRATION.md) for API/wire examples and provider responsibilities.
 
 ## 0.1.0