feat(cu): wire verified backend into desktop

[hqhq1025]

Upstream stack notice

This is stack PR E. It depends on #894 and must not merge before it.

The Files tab is cumulative until preceding fork branches are rebased after merge.

Review the exact 9-file Desktop wiring net diff now in fork-local PR hqhq1025#4.

Current rebase verification: full repository build; Desktop 2416/2416; Desktop typecheck.

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Goal

Wire the verified @maka/computer-use backend into the Desktop host without pulling presentation, provider-specific loops, or cumulative E2E into the same review unit.

What this PR does

• resolves the development and packaged cua-driver artifact locations
• verifies a regular, non-symlink executable against the pinned SHA-256 before backend selection
• requires distributionReady: true in packaged mode while still allowing the verified development artifact
• registers Computer Use tools only when backend selection succeeds
• projects live action/capture service health into Capability Center
• reports scoped target/action-category approval instead of per-action approval
• clears Runtime and executor ownership on stop, archive, remove, terminal turn events, stream errors, and app shutdown
• keeps shutdown cleanup isolated through Promise.allSettled
• builds @maka/computer-use before Desktop tests, build, screenshots, and smoke commands

Reverse-engineering constraints applied

The implementation follows the local Codex Computer Use lab findings:

• approval is a scoped app capability, not evidence that a particular action is valid
• action requires a fresh observation after approval
• user stop, intervention, stale state, and service recovery invalidate prior execution ownership
• service availability is derived from live role state, not binary presence alone
• packaged enablement fails closed while distribution provenance/signing/notarization are incomplete

Relevant lab chapters: wrapper policy/TOCTOU, policy error state machine, service lifecycle, and Electron presentation contract.

Non-goals

• cursor overlay or presentation lifecycle
• provider-specific Computer Use adapters/model loops
• physical intervention, lock/unlock, and blocked-URL host event producers
• deterministic cumulative Electron E2E
• release packaging, Developer ID signing, notarization, SBOM, or artifact attestation
• Headless support

Verification

• npm --workspace @maka/runtime test — 1420 passed, 2 skipped
• npm --workspace @maka/computer-use test — 97 passed
• npm --workspace @maka/desktop run typecheck
• npm --workspace @maka/desktop test — 2392 passed
• git diff --check

Remaining release blocker

Hash verification still precedes path-based process spawn. Packaged release remains disabled until the artifact is distribution-ready; the release chain must additionally bind the verified file identity to the executed canonical artifact and complete signing/notarization/attestation.

Stacked on #3.

[hqhq1025]

@astrohan This Computer Use stack slice is ready for review. Please follow the dependency and merge order stated at the top of the PR; the exact net diff is linked there.

[Astro-Han]

Approved. I found no P0 or P1 on the current head. The physical-input guard is wired through Desktop, the host, and the backend selector, and its error path fails closed. These remaining findings are non-blocking.

P2

1. Computer Use is registered without checking model vision support (apps/desktop/src/main/main.ts:569-589). The app already computes supportsVision later, but does not use it to filter this tool group. Since observe and screenshot return image-data, a non-vision model with function calling can load the tool and fail on the next model request. This needs an availability gate tied to the selected model.
2. smoke:browser still builds only @maka/core before build:main (apps/desktop/package.json:31). In a clean checkout with packages/computer-use/dist absent, it fails with TS2307 for @maka/computer-use. Add the new workspace build to this smoke path.

P3

1. If the backend was selected successfully but the action or capture service later becomes unavailable or disposed, the top-level capability reason still says no integrity-checked artifact was found (apps/desktop/src/main/capability-snapshot.ts:149-160). The runtime probe shows the actual service failure, so this is misleading diagnostics rather than a functional gate failure.

CI is green. The focused Computer Use tests passed, including 108 package tests and 9 Desktop tests. No fix round is required for these items; this PR should merge after #894.

[Astro-Han]

Restack-only rereview on a9aeff4f. The aggregate patch-id exactly matches the reviewed Desktop wiring and physical-input guard commits. Typecheck, test, and e2e are green. No P0 or P1.

P2

1. Computer Use can still be loaded for a non-vision model even though observation results contain image data.
2. The clean smoke:browser path does not build @maka/computer-use before Desktop main and can fail with TS2307.

P3

1. A later cua-driver service failure is described as an artifact-integrity failure in the top-level capability reason.

These findings remain non-blocking. Approved for squash merge with no additional fix round.