Go-live package: Day-0 install runbook + clean-room drill + host-install v1.9.1

- documentation/runbooks/day0-install.md (NEW): operator Day-0 guide, every
  command drill-executed verbatim (Parts A-F incl. the mandatory one-time
  controller update D.1b and the OQ-3 prereq checklist).
- documentation/audits/DRILL-day0-cleanroom-2026-07-03.md (NEW): nested-PVE
  clean-room drill evidence D0-D6, residue tables, OQ-1/2/3 answers, findings
  ledger (B1-B5), go/no-go for Peti (GO).
- scripts/felhom-host-install.sh v1.9.1: residue-free uninstall (agent config,
  shared-parent unit/script/mount, mkfs wrapper, hook snippet, dnsmasq
  snippets; zero-residue diff proven) + post-provision guest reboot (R6) +
  header/version sync.
- CONTEXT.md, REPORT.md, scripts/CHANGELOG.md updated.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PSK5g6qYLknKj8u3QAFEr6

CONTEXT.md

@@ -3,6 +3,18 @@
 > Created with the REUSE.md rollout (2026-07-03). Authoritative history: `hub/CHANGELOG.md` (hub),
 > `website/CHANGELOG.md`, `scripts/CHANGELOG.md`; end-of-task detail in `REPORT.md`.
 
+- **2026-07-03 — GO-LIVE PACKAGE SHIPPED (host-install v1.9.1 + day0-install runbook + clean-room drill)** —
+  `documentation/runbooks/day0-install.md` is the operator Day-0 guide, **every command executed
+  verbatim** on a throwaway nested PVE 9.2.2 (build server): install → verify → app deploy →
+  uninstall → **zero-residue diff** → reinstall. v1.9.1 = residue-free uninstall (agent config w/
+  hub api_key, shared-parent unit/script/mount, mkfs wrapper, hook snippet, dnsmasq snippets) +
+  post-provision guest reboot (without it the controller never deploys on slower hardware) + header
+  sync. Evidence + go/no-go for Peti (**GO**, 3 install-day items):
+  `documentation/audits/DRILL-day0-cleanroom-2026-07-03.md`. Key OQ-2 finding: golden bakes a
+  pre-floor controller 0.85.1 → **fresh installs need the one-time D.1b update** (agent restart →
+  update button → 0.98.3); follow-ups recorded: rebuild golden ≥0.86.0 + re-vouch (operator), agent
+  `mkdir -p` for the guesthook snippet dir, fresh-install local-API 401 (pre-existing), hub has no
+  host-delete path. Drill VM parked virgin-snapshotted on 180 (`~/drill/`).
 - **2026-07-03 — A1 CLOSED (host-install v1.9.0 + agent v0.62.0)** — `Pool.Audit` added to
   `FelhomAgentGuest`; the agent's stale-lock reaper now intersects its scan with
   `GET /pools/felhom` membership (fail-safe skip on read failure). Spike: