feat: stage exact Plugin Tools through shared Worker composition

Extract the unchanged canonical plan model for typed Runtime snapshots without a Server dependency cycle. Bind Tool consumer identities to persisted Session/call IDs, use the owner-issued context and current publication authorization, and register through FeatureInstallPlan with cooperative shutdown.

Validation so far: root cargo check --locked, portable model 6 tests/doctest, Worker actual Component adapter 7 focused tests, Server plan 9 tests via shared isolation. Full product launch owner/pin lifecycle and Remote/Embedded vertical integration remain a subsequent coherent change.

crates/plugin-plan/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "plugin-plan"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+rust-version.workspace = true
+publish = false
+
+[dependencies]
+manifest.workspace = true
+schemars.workspace = true
+serde = { workspace = true, features = ["derive"] }
+serde_json.workspace = true
+sha2.workspace = true
+thiserror.workspace = true