feat: Implement git-crypt lifecycle management and key instructions

lib/git-crypt.sh

@@ -0,0 +1,79 @@
+#!/usr/bin/env bash
+# =============================================================================
+# lib/git-crypt.sh
+# git-crypt lifecycle management (init, export, verify).
+# =============================================================================
+
+gcrypt_init() {
+  git-crypt init
+  success "git-crypt initialized in $(pwd)"
+}
+
+gcrypt_export_key() {
+  local genome_name="$1"
+  local key_path="${KEYS_DIR}/${genome_name}.key"
+
+  mkdir -p "${KEYS_DIR}"
+  git-crypt export-key "$key_path"
+  success "Symmetric key exported to: $key_path"
+  warn "Action required: Store this key in Vaultwarden and remove it from local disk."
+}
+
+gcrypt_verify() {
+  local genome_name="$1"
+  local key_path="${KEYS_DIR}/${genome_name}.key"
+
+  info "Verifying git-crypt status for ${genome_name}..."
+  git-crypt lock
+
+  # Checking if the private marker is still encrypted (binary check)
+  if file "raw/private/.gitkeep" 2>/dev/null | grep -q "data"; then
+    success "Encryption verified: private/ directory is protected."
+  else
+    warn "Encryption check inconclusive. Please run 'git-crypt status' manually."
+  fi
+
+  [[ -f "$key_path" ]] && git-crypt unlock "$key_path"
+}
+
+gcrypt_print_key_instructions() {
+  local genome_name="$1"
+  local v_url="${VAULTWARDEN_URL:-https://your-vaultwarden.com}"
+
+  echo -e "\n  ── ${BOLD}Key Management: ${genome_name}${NC} ──\n"
+  echo "  1. Encode the key to base64:"
+  echo "       base64 < ${KEYS_DIR}/${genome_name}.key"
+  echo ""
+  echo "  2. Save to Vaultwarden (${v_url}):"
+  echo "       Name: \"${genome_name} key\""
+  echo "       Note: <paste the base64 string>"
+  echo ""
+  echo "  3. For AI Server / Runtime Injection:"
+  echo "       export BW_SESSION=\$(bw unlock --raw)"
+  echo "       git-crypt unlock <(bw get notes \"${genome_name} key\" --session \"\$BW_SESSION\" | base64 -d)"
+}
+
+gcrypt_print_runtime_model() {
+  echo ""
+  echo "  RUNTIME SECURITY MODEL:"
+  echo "  ─────────────────────────────────────────────────────────────"
+  echo "  On Forgejo (remote):"
+  echo "    raw/private/ and wiki/private/ are opaque AES-256-CTR blobs."
+  echo "    Collaborators without the key see binary in private/,"
+  echo "    plaintext everywhere else. Git handles this gracefully."
+  echo ""
+  echo "  On your laptop:"
+  echo "    Once unlocked, files are transparently decrypted by the git"
+  echo "    smudge filter. Obsidian reads them as normal Markdown."
+  echo ""
+  echo "  On the AI VM:"
+  echo "    Same as laptop when unlocked. Use runtime injection (step 5"
+  echo "    above) so the key is never written to disk."
+  echo ""
+  echo "  Limitation:"
+  echo "    Encryption does NOT protect against a full server compromise"
+  echo "    where an attacker has root access to a machine where the repo"
+  echo "    is already unlocked. Runtime injection mitigates this."
+  echo "  ─────────────────────────────────────────────────────────────"
+  echo ""
+}