Add `npm run ava` command, update instructions, and exclude files from VSCode search #10436

Job	Run time
analyze-other (actions)	51s
analyze-other (python)	1m 2s
check-codeql-versions	34s
analyze-javascript (ubuntu-22.04)	3m 58s
analyze-javascript (windows-2022, linked)	6m 35s
analyze-javascript (ubuntu-24.04, linked)	3m 58s
analyze-javascript (ubuntu-22.04, linked)	4m 18s
analyze-javascript (macos-13)	7m 22s
analyze-javascript (windows-2025, linked)	6m 20s
analyze-javascript (macos-13, linked)	6m 54s
analyze-javascript (windows-2022)	5m 48s
analyze-javascript (windows-2025)	6m 31s
analyze-javascript (ubuntu-24.04)	4m 15s
analyze-javascript (macos-15)	9m 0s
analyze-javascript (macos-15, linked)	7m 41s
analyze-javascript (macos-14)	7m 30s
analyze-javascript (macos-14, linked)	7m 45s
	1h 30m 22s

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