docs(skills): add the agent-experience skill

Carry the user-scoped agent-experience guidance into the repository unchanged so
project sessions discover it beside the other repository skills. The file,
including its frontmatter, is byte-identical to the personal copy.

.agents/skills/agent-experience/SKILL.md

@@ -0,0 +1,13 @@
+---
+name: agent-experience
+description: Use when designing agent tools, skills, context loading, or multi-step workflows to make information discoverable and use context efficiently.
+metadata:
+  date: "2026-09-11"
+---
+
+- **Start with minimal context:** expose purpose, available actions, and constraints first; load detailed instructions when needed.
+- **Make discovery explicit:** every deferred resource needs a clear description and a reliable way to retrieve it.
+- **Keep critical constraints visible:** permissions, destructive effects, and required validation should appear before the relevant action.
+- **Prefer bounded outputs:** return concise results with identifiers or paths for retrieving details; avoid dumping entire logs or documents.
+- **Use locality:** include a bounded amount of likely needed adjacent context with an operation’s result. For example, deliver a thread reply with a few preceding messages. Mark omissions and truncation explicitly, and provide a way to retrieve more.
+- **Evaluate total work:** saving context is useful only if it does not cause more searches, repeated reads, or mistakes.