fix: edge-control: deregister has no ownership check — any authorized SSH key can take over any project (#1091)

Require the caller to prove ownership on deregister by providing the
pubkey that was used during registration. The stored pubkey is loaded
from registry.json and compared byte-for-byte against the supplied key.

Changes:
- Add get_pubkey() helper to lib/ports.sh
- Update do_deregister() to verify caller pubkey before removing project
- Update SSH protocol to "deregister <project> <pubkey>"
- Update bin/disinto CLI to read tunnel keypair and pass pubkey
- Return {"error":"pubkey mismatch"} on failure (no pubkey leakage)
- Add unit tests for both success and failure paths

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tools/edge-control/register.sh

@@ -7,7 +7,7 @@
 #
 # Usage (via SSH):
 #   ssh disinto-register@edge "register <project> <pubkey>"
-#   ssh disinto-register@edge "deregister <project>"
+#   ssh disinto-register@edge "deregister <project> <pubkey>"
 #   ssh disinto-register@edge "list"
 #
 # Output: JSON on stdout
@@ -30,11 +30,12 @@ usage() {
   cat <<EOF
 Usage:
   register <project> <pubkey>       Register a new tunnel
-  deregister <project>              Remove a tunnel
+  deregister <project> <pubkey>     Remove a tunnel (requires owner pubkey)
   list                              List all registered tunnels
 
 Example:
   ssh disinto-register@edge "register myproject ssh-ed25519 AAAAC3..."
+  ssh disinto-register@edge "deregister myproject ssh-ed25519 AAAAC3..."
 EOF
   exit 1
 }
@@ -104,10 +105,11 @@ do_register() {
   echo "$response"
 }
 
-# Deregister a tunnel
-# Usage: do_deregister <project>
+# Deregister a tunnel — requires ownership proof
+# Usage: do_deregister <project> <pubkey>
 do_deregister() {
   local project="$1"
+  local caller_pubkey="$2"
 
   # Get current port before removing
   local port
@@ -118,6 +120,15 @@ do_deregister() {
     exit 1
   fi
 
+  # Verify caller owns this project (pubkey must match)
+  local stored_pubkey
+  stored_pubkey=$(get_pubkey "$project")
+
+  if [ "$caller_pubkey" != "$stored_pubkey" ]; then
+    echo '{"error":"pubkey mismatch"}'
+    exit 1
+  fi
+
   # Remove from registry
   free_port "$project" >/dev/null
 
@@ -196,13 +207,17 @@ main() {
       do_register "$project" "$pubkey"
       ;;
     deregister)
-      # deregister <project>
-      local project="$args"
-      if [ -z "$project" ]; then
-        echo '{"error":"deregister requires <project>"}'
+      # deregister <project> <pubkey>
+      local project="${args%% *}"
+      local pubkey="${args#* }"
+      if [ "$pubkey" = "$args" ]; then
+        pubkey=""
+      fi
+      if [ -z "$project" ] || [ -z "$pubkey" ]; then
+        echo '{"error":"deregister requires <project> <pubkey>"}'
         exit 1
       fi
-      do_deregister "$project"
+      do_deregister "$project" "$pubkey"
       ;;
     list)
       do_list