Add typed native desktop capability ABI

[wieslawsoltes]

Problem and resulting behavior

Native WebScene hosts need a browser-shaped, versioned boundary for clipboard and desktop window operations. The legacy string request path could not safely carry binary clipboard data, complete awaited operations, bind requests to a realm/navigation generation, or report lifecycle and fullscreen state.

This change adds one typed request/completion ABI shared by both capability families. Clipboard supports Promise-based text and typed MIME/byte operations, ClipboardItem, native copy/cut/paste events, cancellation, stale and duplicate completion rejection, navigation/teardown ownership, bounded queues, and a compatibility fallback. Window capabilities cover external URLs, close, focus, fullscreen enter/exit, visibility/focus/fullscreen publication, and standard events.

Issue mapping

• Closes Add a bounded async Clipboard API host ABI for native runtimes #86: bounded asynchronous Clipboard API host ABI, typed MIME/byte transport, native shortcuts, payload and request-pool bounds, lifecycle cancellation, and 10,000-operation gates.
• Closes Complete host-driven native close veto lifecycle #87: typed external URL/window lifecycle/fullscreen requests and completions, native state publication, standard events, and 10,000-operation request/focus-transition gates.
• Coordinates with SceneTech/AppScene#66 for AppScene host implementation and packaged Code OSS qualification.

The ABI is shared deliberately: clipboard and window operations use the same request identity, completion, realm ownership, cancellation, and queue-bound machinery.

Scope

• One focused commit on current main at 755d88c918bd245f8d29b0a9166e51d656913f85
• Exact head: 4b61f2102c6aa987045d5d3ddd4b0ceb973bf909
• 26 files; stale PR history, the removed documentation file, and the dependent Diagnose native worker crash during legacy clipboard completion #89 diagnostics/teardown layer are excluded
• Generated WebIDL catalog updated deterministically to 21 interfaces and 182 members
• Adds the desktop-host-capabilities focused native filter so this ABI can be qualified without the broad product matrix

Validation

• Release V8 native engine build
• Focused native capability filter: 5/5 passes
• 10,000 focus transitions: 0.17-0.22 ms
• 10,000 typed window requests: 1.0-2.1 ms
• 16 MiB maximum clipboard payload: 79-96 ms
• 10,000 typed clipboard round trips: 34.9-41.2 ms; pending high-water 16; no retained request
• Native binary interop tests: 2/2
• Cumulative Release compatibility architecture tests pass in the dependent local layer
• Native workflow policy tests: 6/6
• WebIDL generator check, shell syntax check, and git diff --check pass

Stack

This is layer 1 of the native desktop capability stack. The cumulative diagnostics/focus layer is validated remotely before the stack is merged atomically. Draft consolidation PR #76 remains open and unmerged.