Add `npm run ava` command, update instructions, and exclude files from VSCode search #10443

Job	Run time
analyze-other (python)	59s
check-codeql-versions	33s
analyze-other (actions)	53s
analyze-javascript (windows-2022, linked)	6m 0s
analyze-javascript (windows-2022)	5m 52s
analyze-javascript (ubuntu-24.04, linked)	4m 2s
analyze-javascript (ubuntu-22.04, linked)	3m 53s
analyze-javascript (ubuntu-22.04)	4m 13s
analyze-javascript (macos-13, linked)	10m 30s
analyze-javascript (macos-13)	5m 42s
analyze-javascript (macos-15)	8m 36s
analyze-javascript (ubuntu-24.04)	3m 56s
analyze-javascript (windows-2025)	5m 55s
analyze-javascript (macos-15, linked)	6m 28s
analyze-javascript (macos-14, linked)	5m 47s
analyze-javascript (windows-2025, linked)	5m 49s
analyze-javascript (macos-14)	6m 27s
	1h 25m 35s

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