orders|length in t-value parses as orders | length, not as a Jinja
length filter. orders is a sale.order recordset; the `length`
identifier resolves to None; Python evaluates
recordset | None and raises TypeError. Use len(orders) instead.
Also documents the gotcha in CLAUDE.md (rule 19) so future templates
don't reach for Jinja-style filters in t-value.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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