Fix Computer Use permissions, passive screenshots and Windows compatibility

[memory-lee]

Summary

Fix the remaining Computer Use onboarding and screenshot issues, and prevent unsupported Computer History entry points on Windows. This branch starts from computer_use and includes only this round of fixes; it does not bring in the unrelated release-branch changes.

• Let native onboarding own the first permission flow, removing duplicate Settings/Accessibility prompts while keeping application operations blocked until authorization.
• Match the running helper to its compiled build identity. Install the development helper at a stable location with a separate development bundle ID, preserve unchanged signed bundles, and keep its visible name Open Computer Use.
• Reconnect the native proxy after the helper's Quit & Reopen. Never replay an action whose result was lost, and require a new user message after authorization. Memmy itself stays open when only its helper restarts.
• Add get_screen_state for passive display observation and guide the agent to use it for screen-reading requests, so it does not open Finder/Recents as a substitute.
• Make Computer History macOS-only across navigation, saved/deep-linked page selections, model synchronization, built-in skills, tools and HTTP routes. Windows Computer Use remains available.
• Mark the default account agent_chat model as TEXT_IMAGE, passing screenshots directly while preserving the existing fallback for explicit image-input rejection.

The patched macOS runtime is built during development and DMG packaging from a pinned MIT-licensed source snapshot. Source preparation is repeatable and preserves compilation caches without retaining old patch-added files. Native CI builds and tests that runtime. Windows/Linux Computer Use packaging remains unchanged.

Validation

Validated on the clean computer_use-based PR worktree:

• Agent: 17 test files, 340 tests passed, covering permissions, MCP, helper resolution, History platform gates, skills and image/fallback paths.
• Frontend: 9 test files, 90 tests passed, including History platform navigation and existing macOS flows.
• Packaging/contracts: 2 test files, 11 tests passed.
• Native source preparation and signed development-installer fixtures: 9 tests passed.
• Swift: 4 build-identity and 8 passive-observation fixture checks passed; both arm64 and x64 release builds and ad-hoc signature verification passed.
• The compiled Swift proxy passed the reconnect/no-replay test against a temporary local socket.
• Frontend, Agent and Electron TypeScript checks passed; shell syntax and git diff --check passed.

The user previously confirmed the repaired development authorization flow and a subsequent screen-reading request. Automated native tests use fixtures; they do not establish signed-installer acceptance on another machine. Windows desktop acceptance and a measured live foreground/Finder-window invariance check remain unverified.

Scope

The screenshot/Base64 token-estimation display issue is intentionally deferred. No global token-counting change, release-version change or unrelated release-branch work is included.

Test organization

• Move the model-sync test to App/frontend/desktop/src/app/tests/.
• Move the native Swift regression sources to tests/open-computer-use/, update source preparation and CI path filters, and document the new location.
• Revalidated the relocated frontend tests (7), source-preparation tests (2), frontend type checking, and Swift identity/observation fixtures (4 + 8). No application behavior changes in this follow-up.