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/memory/MEMORY.md

@@ -225,3 +225,5 @@
 - [Fire #dev-alerts for client/RMM work](feedback_fire_dev_alerts_for_client_work.md) — Howard+Mike watch #dev-alerts Discord for live visibility into what techs/sessions touch. Fire post-bot-alert.sh ([DEV]/[RMM]/[DEPLOY]/[GURURMM] prefix -> #dev-alerts) at the START of any RMM/Dev or active-client-machine action. No CLAUDE.md rule yet — this memory is the rule.
 - [M365 app: SharePoint needs CERT](reference_m365_app_sharepoint_rest_vs_graph.md) — SP app-only works via the CERT (get-token.sh <tenant> sharepoint); the secret gives "Unsupported app only token". Graph app-only uses the secret.
 - [EDR auto-isolates GuruRMM PowerShell](project_edr_rmm_autoisolation_fp.md) — Datto "Exfiltration Over HTTP" rule auto-isolates benign GuruRMM scripts fleet-wide (vwp-qbs 4h outage); watcher + narrow suppression deployed, policy fix pending Mike
+- [Background tasks — no shell `&`](feedback_background_task_no_ampersand.md) — with run_in_background:true, run the command in the foreground of the shell; adding `&`/`disown` forks + exits 0 instantly, orphaning a blocking wait so it never delivers (hit twice building ask-forum)
+- [ask-forum — human-in-the-loop via #ct-forum](../skills/ask-forum/SKILL.md) — ask a teammate a question in the private ct-forum Discord forum, get their human answer back in-session; forum-only, any human can answer, run the --wait as a proper background task