Add local MCP bridge

[pranc1ngpegasus]

Summary

• add a bundled stdio MCP bridge binary (wisp-mcp) for asking about the current Wisp transcript
• add an opt-in local IPC server in the desktop app with a Library-screen toggle and persisted setting
• include wisp-mcp in release app bundles and add artifact_only dispatch mode to the release workflow for local E2E app artifacts

Testing

• cargo fmt --all -- --check
• cargo clippy --workspace --exclude wisp-desktop --all-targets -- -D warnings
• cargo test --workspace --exclude wisp-desktop --all-targets
• cargo check -p wisp-desktop --features gpui/runtime_shaders
• cargo test -p wisp-desktop --features gpui/runtime_shaders ipc_server
• cargo test -p wisp-desktop --features gpui/runtime_shaders settings

Note: desktop checks use gpui/runtime_shaders locally because this machine does not have Xcode metal available.

Local E2E artifact

Run the release workflow manually on this branch with artifact_only=true to upload a DMG/zip artifact without publishing a GitHub Release.