feat: Implement cross-canister plugin calls

[adamspofford-dfinity]

Allows plugins to call canisters other than the one they are assigned to. Canisters must be listed in a canisters list and, if in another project, that project must be a dependency.

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[Copilot]

Pull request overview

Adds permission-controlled cross-canister calls for sync plugins while retaining host-canister targeting.

Changes:

• Adds manifest configuration for allowed canisters.
• Extends the plugin ABI with explicit call targets and runtime enforcement.
• Updates documentation, schemas, examples, and tests.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
examples/icp-sync-plugin/plugin/src/lib.rs	Targets the host canister explicitly.
docs/schemas/icp-yaml-schema.json	Adds the canisters schema field.
docs/schemas/canister-yaml-schema.json	Adds the canisters schema field.
docs/reference/configuration.md	Documents callable-canister configuration.
docs/guides/writing-sync-plugins.md	Explains target selection for authors.
docs/concepts/sync-plugins.md	Describes cross-canister permissions and routing.
crates/icp/src/manifest/canister.rs	Updates manifest test expectations.
crates/icp/src/manifest/adapter/plugin.rs	Parses named and principal canister references.
crates/icp/src/canister/sync/plugin.rs	Resolves declared callable canisters.
crates/icp-sync-plugin/sync-plugin.wit	Adds the call-target ABI field.
crates/icp-sync-plugin/src/runtime.rs	Enforces targets and routes calls accordingly.
crates/icp-sync-plugin/src/lib.rs	Exports callable-canister configuration.
crates/icp-sync-plugin/DESIGN.md	Updates plugin architecture documentation.
crates/icp-cli/src/operations/bundle.rs	Updates bundled plugin adapter construction.

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