ask-forum: promote to a full skill + wire into skill-first routing

Add .claude/skills/ask-forum/SKILL.md (usage contract, correlation model,
forum-only scope, access/permissions) and route to it from CLAUDE.md
(skill-first covered domains) + SKILL_ROUTING.md, so sessions invoke the
skill instead of hand-rolling the Discord API — the footgun that produced a
broken background wait. Capture that footgun as memory
feedback_background_task_no_ampersand (run_in_background, never a shell &).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.claude/SKILL_ROUTING.md

@@ -34,6 +34,7 @@
 | UniFi WiFi tuning / RF / channel analysis | `unifi-wifi` |
 | Map/repoint a Windows network drive on a remote endpoint | `drive-map` |
 | Send someone a Discord DM / copy-paste-friendly link or command | `discord-dm` |
+| Ask a teammate a question/decision/sign-off and get their human answer back in-session | `ask-forum` (run the `--wait` as a proper background task — NO shell `&`) |
 | Inter-session messaging, fleet todos, resource locks, coord status | `coord` |
 | Git / Gitea / submodules / sync health | `gitea` (or `/sync`, `/scc`, `/save` for session ops) |
 | Build/verify GuruRMM agent/server/dashboard, pre-merge check | `gururmm-build` |