fix(web-integration): preserve selection for cut shortcuts

[quanruzhuoxiu]

Summary

• Preserve an existing selection when Copy or Cut targets the already focused element. This is the Playwright Cmd/Ctrl+X fix because the previous coordinate click collapsed the selected range before the shortcut.
• Map Cmd/Ctrl+X to the CDP Cut editing command for Puppeteer. Playwright does not consume explicit editing commands through its public keyboard API, so this is an independent Puppeteer improvement.
• Keep the target-focus contract by clicking when a different element owns focus.

Independent regression proof

• Playwright focus behavior: verify that selection-preserving focus keeps the full selected range, while the previous coordinate click collapses it.
• Command mapping: verify that Cmd/Ctrl+X produces the explicit Cut editing command.
• Puppeteer command behavior: use a non-cut function key to prove that adding the explicit Cut command changes real Chromium behavior from preserving the selected value to cutting it, without invoking target-focus logic.
• Puppeteer end to end: run Cmd/Ctrl+A followed by Cmd/Ctrl+X against the same target, assert that the full range remains selected before Cut, the value is removed, and Chromium emits a cut event.
• Keep end-to-end Playwright coverage for select-all, copy, cut, and wrong-focus boundaries.

Review findings resolved

• Separate the two behavioral changes so each has an independent failing boundary and passing assertion.
• Prevent Copy/Cut from acting on the wrong element when another input owns focus.
• Keep the new focus capability optional for Chrome Extension and Bridge structural adapters.
• Expand and rename the editing-command test suite to match its responsibility.

Validation

• pnpm run lint
• pnpm --filter @midscene/web exec vitest --run tests/unit-test/base-page-editing-commands.test.ts tests/unit-test/util.test.ts (26 passed)
• pnpm --filter @midscene/web exec vitest --run --coverage tests/unit-test/base-page-editing-commands.test.ts tests/unit-test/util.test.ts (26 passed)
• pnpm exec tsc -p packages/web-integration/tsconfig.json --noEmit --pretty false
• pnpm exec nx test @midscene/web (428 passed, 1 skipped)
• pnpm exec nx build @midscene/web
• git diff --check