feat: alkcall 0.9.0 adoption — bump to 0.7.0

The stub-sweep release changes no type alktty touches: the four
implemented stubs, the register_openable Pub-typed refusal (alktty's
op is Sub-typed), the register_imported Result return, and the removed
RelayError::PubTypedOpen are all surfaces alktty never exercises.

- alkcall requirement 0.8.1 -> 0.9.0; lockfile follows
- alktty 0.6.0 -> 0.7.0 (minor: raising the minimum alkcall requirement
  is ecosystem-coordination breaking on a 0.x crate)
- one test fix: `establisher_ok_on_valid_params` formatted a
  Result<Establishment, _> with {:?} — Establishment no longer derives
  Debug in alkcall 0.9.0; the assert now branches on Err and formats
  only the error

Verification: 113 default / 156 all-features tests, clippy
--all-targets -D warnings, fmt --check, cargo doc, fuzz corpus replay
(9 tests / 340 seeds), wasm32-unknown-unknown check + clippy,
publish --dry-run — all pass.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "alktty"
-version = "0.6.0"
+version = "0.7.0"
 edition = "2021"
 rust-version = "1.88"
 license = "MIT OR Apache-2.0"
@@ -29,7 +29,7 @@ default = []
 local = ["dep:portable-pty", "dep:tokio-util", "tokio/process", "tokio/rt-multi-thread"]
 
 [dependencies]
-alkcall = "0.8.1"
+alkcall = "0.9.0"
 # Minimal, wasm-clean tokio features. `local` adds `process` +
 # `rt-multi-thread` (non-wasm). Do NOT use `features = ["full"]` — it
 # pulls in `signal`/`fs`/`net` which break `wasm32-unknown-unknown`.