Add verification claude skill for parsedmarc CLI usage and sample inputs

.claude/skills/verify/SKILL.md

@@ -0,0 +1,46 @@
+---
+name: verify
+description: Launch and drive parsedmarc's CLI to verify parser/output changes end-to-end against the bundled sample reports.
+---
+
+# Verifying parsedmarc changes
+
+The runtime surface is the `parsedmarc` CLI; the library's stream APIs are
+drivable via `python -c` through the public `parsedmarc` package.
+
+## Launch
+
+```bash
+# No config file → results print as JSON to stdout. --offline skips DNS/downloads.
+GITHUB_ACTIONS=true .venv/bin/python -m parsedmarc.cli --offline <sample files>
+```
+
+- Do **not** use `-c ci.ini` locally: it points at `http://localhost:9200`
+  Elasticsearch (a CI service container) and retries for ~75s before failing.
+- `GITHUB_ACTIONS=true` skips live DNS lookups.
+- `--debug` surfaces per-file parse warnings/errors (invalid reports are
+  otherwise dropped silently from the JSON).
+
+## Good sample inputs (all under `samples/`)
+
+- `aggregate/rfc9990-sample.xml` — RFC 9990 aggregate report
+- `aggregate/*.xml.zip`, `aggregate/*.xml.gz` — archive extraction paths
+- `failure/dmarc_ruf_report_linkedin.eml` — failure (RUF) report with an
+  embedded rfc822 sample (exercises `utils.parse_email`)
+- `aggregate/invalid_xml.xml` — recovered via lxml, parses with `errors` set
+
+## Stream API (stdin is genuinely non-seekable when piped)
+
+```bash
+cat samples/aggregate/*.xml.gz | .venv/bin/python -c \
+  "import sys, parsedmarc; print(parsedmarc.extract_report(sys.stdin.buffer)[:80])"
+# Text-mode stdin must raise ParserError ("binary (rb) mode"):
+cat samples/extract_report/nice-input.xml | .venv/bin/python -c \
+  "import sys, parsedmarc; parsedmarc.extract_report(sys.stdin)"
+```
+
+## Gotchas
+
+- Parse failures are WARNING-level log lines, not stderr errors — grep the
+  `--debug` output; the JSON just omits the report.
+- To compare against unfixed code: `git stash push -- <file>`, run, `git stash pop`.