feat: add managed skills gating

skills/bird/SKILL.md

@@ -0,0 +1,19 @@
+---
+name: bird
+description: X/Twitter CLI to tweet, reply, read threads, and search.
+metadata: {"clawdis":{"requires":{"bins":["bird"]}}}
+---
+
+# bird
+
+Use `bird` to interact with X/Twitter.
+
+- Tweet: `bird tweet "..."`
+- Reply: `bird reply <tweet-id> "..."`
+- Read: `bird read <tweet-id>`
+- Thread: `bird thread <tweet-id>`
+- Search: `bird search "query"`
+- Mentions: `bird mentions`
+- Whoami: `bird whoami`
+
+Confirm before posting publicly.