Add `npm run ava` command, update instructions, and exclude files from VSCode search #10442

Job	Run time
check-codeql-versions	38s
analyze-other (actions)	55s
analyze-other (python)	1m 1s
analyze-javascript (macos-14)	7m 2s
analyze-javascript (windows-2022)	6m 5s
analyze-javascript (macos-14, linked)	8m 3s
analyze-javascript (windows-2022, linked)	6m 25s
analyze-javascript (macos-13)	6m 5s
analyze-javascript (ubuntu-22.04, linked)	3m 55s
analyze-javascript (ubuntu-24.04, linked)	3m 55s
analyze-javascript (macos-15, linked)	8m 22s
analyze-javascript (ubuntu-22.04)	4m 6s
analyze-javascript (macos-13, linked)	9m 23s
analyze-javascript (windows-2025, linked)	6m 4s
analyze-javascript (ubuntu-24.04)	4m 15s
analyze-javascript (windows-2025)	6m 45s
analyze-javascript (macos-15)	6m 32s
	1h 29m 31s

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