Initial: pi-skill — 68 skills, 43 extensions, 11 themes for Pi

skills/references/type-sequence.md

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+# Sequence
+
+**Best for:** request/response flows, protocol exchanges, multi-actor interactions over time, API call traces, incident reconstructions.
+
+## Layout conventions
+- Actors as boxes in a horizontal row at the top.
+- **Lifelines**: dashed vertical lines descending from each actor to the bottom.
+- Messages: horizontal arrows between lifelines; time flows top→down.
+- **Activation bar**: narrow rectangle (`w=8`, muted fill, 0.8 hairline stroke) on a lifeline spanning the interval that actor holds control. Stack for nested calls.
+- Self-messages: short U-shaped loop returning to the same lifeline; label right of the loop.
+- Return messages: dashed line in the same color as the originating call.
+- Coral on the primary success response or headline message — one, maybe two.
+
+## Anti-patterns
+- Message arrow pointing *upward* (reverses time — never).
+- Activation bars that never close.
+- Labels sitting over another lifeline — shorten or shift y into a gap.
+- Swimlane-style lanes instead of lifelines (different grammar).
+
+## Lifeline primitive
+```svg
+<line x1="CX" y1="TOP" x2="CX" y2="BOTTOM"
+      stroke="rgba(11,13,11,0.20)" stroke-width="1" stroke-dasharray="3,3"/>
+```
+
+## Activation bar primitive
+```svg
+<rect x="CX-4" y="TOP" width="8" height="H"
+      fill="rgba(11,13,11,0.06)" stroke="#52534e" stroke-width="0.8"/>
+```
+
+## Examples
+- `assets/example-sequence.html` — minimal light
+- `assets/example-sequence-dark.html` — minimal dark
+- `assets/example-sequence-full.html` — full editorial