docs(wiki): firmware/dbx-vs-TPM hardening + create disk-os-hardening page

Real-world park-buzi episode: a UEFI dbx update (delivered via fwupd/LVFS,
NOT apt) revoked a stale GRUB -> panic, and moved PCR 7 -> broke TPM-sealed
LUKS auto-unlock -> passphrase prompt. Recovered by re-sealing PCR 7.

- appliance-provisioning.md: extend the §4 re-seal runbook to name dbx; new
  §4a (fwupd-not-apt, GRUB-panic ordering, PCR-7 re-seal, operator lockdown:
  mask fwupd + remove firmware-updater snap + BIOS-password + passphrase
  escrow) incl. the --test-passphrase-silently-passes-via-TPM trap
  (--disable-external-tokens); gotchas #12/#13.
- disk-os-hardening.md: NEW — resolves a long-dangling wikilink referenced
  from ~18 pages. The *why* of host hardening (5 controls + firmware lockdown);
  commands stay in appliance-provisioning; reconciliation remains the primary
  anti-fraud control.
- index.md: expand the disk-os-hardening catalog line.
- log.md: two note entries.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

wiki/index.md

@@ -55,7 +55,7 @@ Counts: 4 sources · 19 entities · 46 concepts · 7 decision records.
 ## Concepts — integrity & anti-fraud
 - [[append-only-event-chain]] — append-only + hash chain + ATECC608 signing = unforgeable log.
 - [[reconciliation]] — the real anti-fraud control; what remote sync actually is.
-- [[disk-os-hardening]] — LUKS/GRUB/Secure Boot; worthwhile but not the main event.
+- [[disk-os-hardening]] — the *why* of host hardening: LUKS FDE + TPM-sealed auto-unlock (PCR 7) + Secure Boot + GRUB edit-lock + unprivileged operator + firmware/dbx lockdown; secondary control (reconciliation is the main event). Commands → [[appliance-provisioning]].
 - [[backup-recovery]] — admin-driven encrypted full-DB backup (local/SMB/SFTP) + DR; signing key escrowed & decoupled from TPM so the ledger survives total hardware loss; restore is admin-only.
 
 ## Concepts — device architecture & safety