docs(skills): add run-session skill

Covers the per-turn procedure: bootstrap, intent, deciding to roll, the
CLI, appending a scene, and applying state, with a session template.

.agents/skills/run-session/templates/session.md

@@ -0,0 +1,24 @@
+# Session NNNN — <title>
+
+- **Campaign:** <name>
+- **Game:** <game>
+- **Date:** <YYYY-MM-DD>
+- **PC:** <pc>
+
+## Scene 1 — <title>
+
+> **Player:** <the player's words, verbatim>
+
+`<cli output, verbatim, in backticks>` · `<complication, if any>`
+
+**Resolution:** <what actually happens, in the fiction>
+
+**State:** <every mechanical change, e.g. supply 5 → 4; clock "Gate breached" 1/4>
+
+## Scene 2 — <title>
+
+> **Player:** <the player's words, verbatim>
+
+**Resolution:** <what actually happens, in the fiction>
+
+**State:** <mechanical changes, or omit the line if there were none>