refactor(canvas): make the panel a widget presenter (#126030)

* refactor(canvas): retire legacy host and commands

* refactor(apple): narrow shared Canvas contracts

* refactor(macos): keep Canvas as widget presenter

* refactor(ios): remove Canvas client

* refactor(android): remove Canvas client

* refactor(linux): remove Canvas client

* fix(ci): isolate native locale artifacts

* fix(linux): regenerate companion lockfile

* fix(canvas): refresh native tool display metadata

* test(canvas): align coverage with presenter surface

* test(canvas): remove obsolete asset root seam

* test(canvas): stabilize retirement CI coverage

* refactor(swift): remove orphaned resource wrapper

* test(ios): remove retired canvas layout assertion

* fix(macos): reserve retired canvas command namespace

* refactor(macos): isolate canvas command policy

* fix(canvas): select only eligible macOS panels

* fix(canvas): keep panel selection plugin-owned

.github/labeler.yml

@@ -253,7 +253,6 @@
       - any-glob-to-any-file:
           - "apps/linux/**"
           - "docs/platforms/linux.md"
-          - "extensions/linux-canvas/**"
 "app: web-ui":
   - changed-files:
       - any-glob-to-any-file: