chore(release): 0.9.0 — the stub sweep

- version 0.8.1 -> 0.9.0 (minor bump: 5 breaking lints vs 0.8.1 —
  ManagerError::InvalidAdopt variant, RelayError::PubTypedOpen
  removal, register_imported* Result return, Establishment Debug
  derive dropped; all pre-1.0 permitted)
- CHANGELOG 0.9.0: S-01..S-04 from reviews 010/011 (the marked-pub
  open contract, channel/control, channel/resources/subscribe,
  op/register forward-through), the stub guard, and the
  verification summary
- open_pub_channel: a non-object input tears down the freshly
  allocated id before the early return (the slot is not parked
  against the ADR-040 bound; regression test added)
- register_imported_all: atomic — a refusal leaves the overlay
  untouched; atomicity documented

Verified: cargo test (697 + stub guard), clippy --all-targets
--all-features -- -D warnings, fmt --check, cargo doc,
wasm32-unknown-unknown check, fuzz corpus replay 5/5,
cargo publish --dry-run --allow-dirty clean.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "alkcall"
-version = "0.8.1"
+version = "0.9.0"
 edition = "2021"
 rust-version = "1.88"
 license = "MIT OR Apache-2.0"