[code-infra] Add flakyness analyzer skill

[Janpot]

Fetches recent CircleCI failure data into a directory of plain-text files and walks the LLM through grep-based pattern discovery to bucket failures into fixable flake, external outage, or real bug. output and cache live under .claude/cache/ (gitignored).

Sample output

gh/mui/mui-x master — last 7 days

64/252 workflow runs failed (25.4% failure rate). 69 failed jobs classified.

Fixable flake (88%):

• 49 times, 71%, browser page crashed mid-test (vitest browser session lost), example
• 7 times, 10%, failed to connect to browser session within timeout, example
• 3 times, 4%, hung job — "Too long with no output (10m)", example
• 1 time, 1%, tsc forced-termination during @mui/x-charts:build, example
• 1 time, 1%, timing race in dataSourceTreeData.DataGridPro revalidate test, example

External outage (6%):

• 4 times, 6%, archive.ubuntu.com unreachable during apt install of ffmpeg, example

4 real issues (not flaky) — pnpm proptypes drift not committed (generated propTypes out of sync with source). Same root cause across the 4 hits, fix is to run pnpm proptypes and commit.

Bottom line: the failure rate on master is dominated by vitest browser-test instability (~80% of failures are page crashes or browser-session timeouts) — retries will green most runs, but this needs a real investigation into vitest
browser flakiness. Everything else is small and well-understood.

[code-infra-dashboard]

Deploy preview

https://deploy-preview-1447--mui-internal.netlify.app/

Bundle size

Total Size Change: 0B^(0.00%) - Total Gzip Change: 0B^(0.00%)
Files: 29 total (0 added, 0 removed, 0 changed)

Show details for 29 more bundles

@mui/internal-docs-infra/abstractCreateDemo parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/abstractCreateDemoClient parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/abstractCreateTypes parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/CodeControllerContext parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/CodeExternalsContext parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/CodeHighlighter parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/CodeHighlighter/errors parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/CodeHighlighter/types parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/CodeProvider parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/createDemoData parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/createDemoData/types parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/createSitemap parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/createSitemap/types parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/useCode parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/useCodeWindow parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/useCopier parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/useDemo parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/useErrors parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/useLocalStorageState parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/usePreference parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/useScrollAnchor parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/useSearch parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/useSearch/types parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/useType parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/useTypes parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/useUrlHashState parsed: 0B^(0.00%) gzip: 0B^(0.00%)
@mui/internal-docs-infra/withDocsInfra parsed: 0B^(0.00%) gzip: 0B^(0.00%)
createParseSourceWorkerClient parsed: 0B^(0.00%) gzip: 0B^(0.00%)
grammars parsed: 0B^(0.00%) gzip: 0B^(0.00%)

Details of bundle changes

Performance

Total duration: 13.43 ms -2.50 ms^(-15.7%) | Renders: 4 ⁽⁺⁰⁾ | Paint: 65.99 ms -2.16 ms^(-3.2%)

Test	Duration	Renders
HeavyList mount	7.28 ms ▼-2.38 ms(-24.6%)	1 (+0)

2 tests within noise — details

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[michelengelen]

looking good ... might prove more useful than my local skill i added because of the ci reports being fetched! :D