`workflow add` gated the local-file branches on a case-SENSITIVE
`.suffix in (".yml", ".yaml")` (the `--dev` branch and the plain
local-path branch), while every other YAML-file detector in the CLI
normalizes case: `workflow run` uses `source_path.suffix.lower()` and
`WorkflowEngine.load_workflow` uses `path.suffix.lower()`.
The result was an add/run inconsistency: `specify workflow run Sample.YAML`
loads the file, but `specify workflow add Sample.YAML` does not recognize
it as a local workflow — the `--dev` branch rejects it with "--dev source
must be a workflow YAML file ..." and the plain path falls through to a
catalog lookup that fails with "not found in catalog".
Add `.lower()` to both suffix reads so `workflow add` matches its siblings.
The lowercase happy path is unchanged.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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