ci: concise Discord release notes and faster spec-sync confirmation

[cahaseler]

Problem / Motivation

Two complaints about the client's #patch-notes post: it arrives long after the gameserver release, and it "says nothing useful."

• Useless message: the Discord body was the auto-generated sync commit — a machine OpenAPI path diff (Paths: N -> M, (Schema-only change; no paths added or removed.)).
• Slow: the release only rides the throttled */30 cron (GitHub spaces it 66–130 min), and when a change is detected the sync-spec run itself burned up to ~16 min (947s in one real run) in an obsolete "wait for version live" poll left over from the async-Render era. The 5-platform build is not the bottleneck — the whole release.yml pipeline is ~60–80s.

Technical Approach

• release.yml (notify job): drop the path-diff dump; post a concise embed — "Updated to match SpaceMolt gameserver vN" (read from the checked-out openapi.json info.x-gameserver-version) with a link to the client's own GitHub Release. No build restructuring — the post already runs after the Release exists.
• sync-spec.yml: trim the "wait for version live" poll from 20×60s to a 5×30s bounded confirmation and fix the stale Render-era comment. Safe because the gameserver's on-box deploy now dispatches only after /health confirms the version live, so the first probe essentially always matches. The changed==true gate (post only when the spec surface actually changed) is unchanged.

Both the trigger reliability (the dispatch now firing at all) and adding spacemolt-lib to the nudge are handled in the dev-harness deploy.sh PR. Requires the existing DISCORD_WEBHOOK_URL repo secret to point at #patch-notes.

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