make-spec — HTML design-doc scaffold (P18 Category-C)

One template + one theme + one filename convention — so the writer spends 100% of energy on substance, 0% on boilerplate.

Why this skill exists

Since P18's promotion 2026-05-13, the workspace produces substantive design docs as native HTML rather than markdown:

Type	Location	Examples (last 7d)
Spec	`docs/specs/`	`2026-05-22-broker-selection-cross-asset.html`, `2026-05-23-life-houston-runtime-integration.html`
Plan	`docs/plans/`	`2026-05-22-feature-flag-design.html`, `2026-05-22-houston-advanced-settings.html`, `2026-05-22-houston-developer-mode.html`
Report	`docs/reports/`	`2026-05-22-houston-dogfood-pattern.html`, `2026-05-22-mission-control-vs-houston.html`
ADR	`docs/adrs/`	(folder reserved; pattern proven via broker-selection ADR in `docs/specs/`)
PR explainer	`docs/pr-explainers/PR-<n>.html`	(P18-reserved path)