feat(computer-use): rebuild scoped control and batched native input

[bobleer]

Summary

Rebuild Computer Use around scoped control sessions, typed batched actions, persistent window observation, and native platform input adapters. Application tasks default to background control; delegated prompts cannot silently authorize foreground takeover.

Type and Areas

Feature, bug fix, refactor, tests and CI dependencies. Rust contracts/core, Desktop native adapters, agent prompts, AI image transport and Web UI control feedback.

Motivation / Impact

Computer Use previously interrupted foreground work, rejected ordinary background pointer actions, lost visual context and encouraged slow single-action loops. This change adds shared single/batch execution with explicit receipts, observation freshness and cancellation, preserves multimodal screenshots, and supplies compact batch examples to the model.

macOS uses persistent window capture and window-directed input with target-local focus, explicit modifiers and process-identity cleanup. Windows uses window capture and UIA/window-message adapters; Ubuntu uses AT-SPI and negotiated portal/PipeWire capabilities. Unsupported operations report their actual limits instead of silently taking over the foreground. The UI exposes control status, stop and pointer feedback. No application-specific WeChat workflow is added.

Verification

• cargo build --locked -p openbitfun-desktop: passed locally on macOS.
• cargo test --locked -p openbitfun-desktop --lib computer_use: 143 passed, 9 native fixtures intentionally ignored in the unit invocation.
• Focused Core Computer Use tool tests: 45 passed; prompt catalog tests: 8 passed.
• node scripts/test-macos-input-controls.mjs: passed against dedicated native test apps.
• node scripts/test-macos-input-controls.mjs --orchestration: passed through the production Tool pipeline. A five-action batch on an occluded non-AX canvas completed in 466 ms including final observation, excluding model reasoning. It preserved the observer's foreground/key/stacking state and physical cursor, delivered one content click, typed into the correct destination, executed a real menu shortcut, scrolled and cleaned up on Stop.
• Repository hygiene, GitHub configuration, core boundaries, i18n and all 23 theme/color surfaces: passed.
• Capability catalog check and 15 capability contract tests: passed after registering status/preview/stop and regenerating remote command maps.
• Frontend production build: passed. Full Web UI suite using CI's Node 22.23.2: 850 files / 9229 tests passed. The local Node 26 run exposed storage-environment differences; no test expectations were weakened.
• Final head f98bbb29cc64149a0ffd3c637310db489ed2eddb: all 15 PR checks passed, including three-platform Rust/CLI, frontend, Linux x64/ARM64 binary and installer validation. CI run.

Reviewer Notes

Architecture and acceptance boundaries are documented in docs/architecture/computer-use-control.md. Native macOS focus uses dynamically resolved private APIs and needs broader application/OS compatibility testing; capability or permission failures must not silently activate apps. The macOS fixtures are local native evidence, not Windows/Ubuntu native or remote-workspace, remote-control, peer-device or detached-dispatch acceptance. Existing Windows/Linux compile/unit evidence is recorded in the spec.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.