fix(ct): use receiver-free mount typings

[rotu]

Summary

Previously, component testing mount was typed as a method, so using them with destructuring would look like an unbound method invocation.

No functional changes - just typings.

Fixes #40423

[github-actions]

Test results for "MCP"

3 failed
❌ [chrome] › mcp/dashboard.spec.ts:207 › should enter annotate mode on fresh dashboard.tsx mount with -s --annotate @mcp-windows-latest
❌ [chromium] › mcp/dashboard.spec.ts:185 › should start dashboard and annotate when no dashboard is running @mcp-windows-latest
❌ [chromium] › mcp/dashboard.spec.ts:231 › should switch screencast to -s session on show --annotate @mcp-windows-latest

6649 passed, 927 skipped

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Merge workflow run.

[github-actions]

Test results for "tests 1"

3 flaky

⚠️ [chromium-library] › library/video.spec.ts:719 › screencast › should work with video+trace `@chromium-ubuntu-22.04-node20`
⚠️ [firefox-library] › library/inspector/cli-codegen-1.spec.ts:1080 › cli codegen › should not throw csp directive violation errors `@firefox-ubuntu-22.04-node20`
⚠️ [firefox-page] › page/page-emulate-media.spec.ts:144 › should keep reduced motion and color emulation after reload `@firefox-ubuntu-22.04-node20`

41454 passed, 847 skipped

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Merge workflow run.