fix: honest remediation batch 3 - fix broken claims and real Argon2id

Previous commits marked findings as ✅ that were actually superficial or
broken. This commit fixes the real problems honestly.

Real fixes:
- Argon2id KDF: Fixed via preseed partman/early_command that patches
  partman-crypto's cryptsetup luksFormat to include --pbkdf argon2id.
  Previous luks-kdf-configure.sh "auto-conversion" was dead code
  (cryptsetup luksConvertKey needs stdin passphrase, nothing provides it).
  Now the hook is an honest verifier, not a fake converter.
- src/security-hardening.sh: Removed sshd_config generation entirely
  (was still generating it despite claiming client-only)
- AIDE init: Removed || true error swallowing, now reports failures
- COMPLIANCE.md: Marked CMMC L3 and FedRAMP as aspirational targets
  with honest explanation of what's missing (3PAO, org controls)
- VERIFICATION-REPORT.md: Added self-review warning about contradictions,
  fixed wrong preseed path (config/preseed.cfg → includes.installer/)
- Removed phantom knel-compliance-check.sh reference from COMPLIANCE.md
- encryption-setup.sh: README now says "Argon2id (via early_command)"
  instead of bare "Argon2id" which was false
- demo.preseed.cfg: Added same Argon2id early_command
- Added .dockerignore (was missing)
- Fixed .gitignore *key* pattern (too broad, matched keyboard.conf etc)

Still remaining (honest assessment):
- C-06: Git history scrub (needs git-filter-repo, destructive)
- H-09: Build cache integrity (design work needed)
- M-11: Docker base digest pinning
- Phase 3: Test suite overhaul (85% grep-based, not behavioral)
- Phase 4: Documentation cleanup (threat model, etc)
- ISO NOT rebuilt since fixes

786 tests pass, 0 shellcheck warnings.

💘 Generated with Crush

Assisted-by: GLM-5.1 via Crush <crush@charm.land>

src/security-hardening.sh

@@ -84,33 +84,16 @@ EOF
   echo "SSH client configuration created at $output_file"
 }
 
-# Function to configure SSH hardening (server config as defense-in-depth)
-# System is SSH client-only per PRD FR-006, but sshd_config is hardened defensively
+# Function to ensure no SSH server configuration exists
+# PRD FR-006: Client-only system. No sshd_config should ever exist.
 configure_ssh() {
   local output_file="${1:-/etc/ssh/sshd_config}"
 
-  cat >"$output_file" <<'EOF'
-# SSH Server Hardening Configuration (defense-in-depth)
-# Reference: PRD FR-006 - Client-only system, sshd not installed
-# This config exists as a security baseline if sshd is ever installed
-
-# Protocol
-Protocol 2
-
-# Authentication
-PermitRootLogin no
-PermitEmptyPasswords no
-MaxAuthTries 3
-
-# Session
-ClientAliveInterval 300
-ClientAliveCountMax 2
-
-# Forwarding
-X11Forwarding no
-EOF
-
-  echo "SSH hardening configuration created at $output_file"
+  # Remove any existing sshd_config to prevent accidental activation
+  if [[ -f "$output_file" && "$output_file" == /etc/ssh/sshd_config ]]; then
+    rm -f "$output_file"
+  fi
+  echo "SSH server config removed per PRD FR-006 (client-only system)"
 }
 
 # Function to configure password policy