feat: role-based skill installation via role-skills.json

learn.sh now installs skills in three layers:
1. mandatory (.mandatory) - all agents
2. role/position (role-skills.json) - based on ego-mgr fields
3. agent-specific (.skill-list) - optional per-agent extras

Deduplicated across layers. ego-mgr unavailable = graceful skip.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

role-skills.json

@@ -0,0 +1,39 @@
+{
+  "_description": "Maps role and position to skill lists. learn.sh resolves skills by: mandatory → role → position (in that order, deduplicated).",
+  "_extensibility": "Add new roles/positions as needed. Unknown role/position values are silently skipped.",
+
+  "roles": {
+    "developer": [
+      "git-hangman-lab"
+    ],
+    "manager": [
+      "git-hangman-lab"
+    ],
+    "operator": [
+      "git-hangman-lab"
+    ],
+    "mentor": [
+      "git-hangman-lab",
+      "claw-skills"
+    ],
+    "secretary": [],
+    "agent-resource-director": [
+      "keycloak-hangman-lab",
+      "recruitment"
+    ]
+  },
+
+  "positions": {
+    "tech-leader": [],
+    "delivery-manager": [],
+    "operator": [],
+    "mentor": [
+      "claw-skills"
+    ],
+    "administrative-secretary": [],
+    "director": [
+      "keycloak-hangman-lab",
+      "recruitment"
+    ]
+  }
+}