docs: record hosted-beta waitlist triage for Metafor (#74)

[CompleteDotTech]

Summary

Adds one dated status/decision record — docs/2026-08-30-hosted-beta-waitlist-metafor.md — triaging the first hosted-beta waitlist intake (issue #74, Metafor, team of 1, BYOM with OSS models) against main @ 8487d1e.

• What exists on main today, with evidence + dates: all six hosted beta code gates shipped (HOSTED.md, 2026-07-08); hosted deploy runbook + deploy/hosted/ stack (2026-07-08); pricing tier proposal with BYOM-everywhere principle (2026-07-07, last touched 2026-07-14); Marketplace listing runbook (2026-07-08); reference demo (2026-07-06); landing page + waitlist issue Ship opencoven.ai/github landing page and hosted beta waitlist #16 closed as completed 2026-07-08 outside this repo (ROADMAP/backlog-dag one day stale on that).
• Verdict: the issue's asks ("what would you assign first?", "find out more") are answerable from main — first assignment = a low-risk maintenance issue (dependency bump / docs fix) assigned to the familiar; no code gap blocks onboarding.
• What remains: operational deployment per the runbook, restore drill, pricing open decisions 1–2, the unanswered intake question (repos/backlog shape), and OSS-model compatibility confirmation (a coven-code concern, outside this repo).
• Also includes the onboarding prep checklist and a draft outreach message (not sent).

Docs-only change (one new file, +175/−0). No code touched.

Issue

Refs #74

Test plan

• Ran locally: relative-link validation for the new doc (all 11 resolve), git diff --check clean
• Ran locally: verified issue/PR states and dates via REST against upstream (issues/74, #16/#17/#19, timeline cross-references)
• Deferred to CI: cargo check --all-targets, cargo clippy --all-targets -- -D warnings, cargo test --all (no Rust toolchain in the authoring environment)
• Deferred to CI: hosted adapter py_compile + unittest (no python3 in the authoring environment)

Vehicle note: opened in the fork CompleteDotTech/coven-github as the CI vehicle — this token cannot write to OpenCoven/coven-github. Re-target upstream once write access is restored. Refs #74.

CI note: no CI exists on this vehicle — .github/workflows/ci.yml is present in the tree, but the fork has zero registered workflows (actions/workflows total_count = 0) and the head commit has zero check-runs 11+ minutes after PR creation (observed 2026-08-30T15:50Z). The cargo and Python gates in the checklist above have therefore run nowhere: not locally (no Rust/python toolchain) and not in CI. Treat green-ness as unverified until the PR is re-targeted upstream.