feat(#88): detect & migrate removed CLI flags into env (ssh-mcp v2)

ssh-mcp v2 removed --password from the command line and reads
SSH_MCP_PASSWORD instead, so an old config crashes on startup. Add a
data-driven FLAG_ENV_MIGRATIONS registry plus detect_migratable_package,
migrate_removed_flags and removed_flag_warnings in bcc_core, and a
'Fix: move to environment variables' one-click action + warning in the
stdio server editor, with a matching main-window lint line. The literal
value lands in env{} (the only form Claude Desktop honours). 14 tests.

bcc.py

@@ -602,6 +602,19 @@ class ServerEditor(QFrame):
         self.secret_warn.setWordWrap(True)
         self.secret_warn.hide()
         v.addWidget(self.secret_warn)
+        # Shown when args carry a CLI flag a package removed in a major version
+        # (e.g. ssh-mcp v2's --password), with a one-click move into env.
+        self.removed_flag_warn = QLabel("")
+        self.removed_flag_warn.setStyleSheet(f"color: {WARN};")
+        self.removed_flag_warn.setWordWrap(True)
+        self.removed_flag_warn.hide()
+        self.removed_flag_fix_btn = QPushButton("Fix: move to environment variables")
+        self.removed_flag_fix_btn.clicked.connect(self._fix_removed_flags)
+        self.removed_flag_fix_btn.hide()
+        rf_row = QHBoxLayout()
+        rf_row.addWidget(self.removed_flag_warn, 1)
+        rf_row.addWidget(self.removed_flag_fix_btn)
+        v.addLayout(rf_row)
         v.addWidget(self._lbl("Environment variables"))
         self.env = KeyValueTable(
             "Variable", "Value", on_change=self._emit, before_change=self._before_change
@@ -649,6 +662,8 @@ class ServerEditor(QFrame):
             self.args_warn.hide()
             self.args_fix_btn.hide()
             self.secret_warn.hide()
+            self.removed_flag_warn.hide()
+            self.removed_flag_fix_btn.hide()
             self._loading = False
             return
         self.setEnabled(True)
@@ -736,6 +751,8 @@ class ServerEditor(QFrame):
             self.args_warn.hide()
             self.args_fix_btn.hide()
             self.secret_warn.hide()
+            self.removed_flag_warn.hide()
+            self.removed_flag_fix_btn.hide()
             return
         _, notes = core.split_suspicious_args(self._current_arg_lines())
         if notes:
@@ -751,6 +768,23 @@ class ServerEditor(QFrame):
             self.secret_warn.show()
         else:
             self.secret_warn.hide()
+        # Flags a package removed across a major version (e.g. ssh-mcp v2's
+        # --password). Needs command + env too, so build from the live form.
+        stdio = {
+            "command": self.command.text().strip(),
+            "args": self._current_arg_lines(),
+            "env": self.env.dump(),
+        }
+        rf_warnings = core.removed_flag_warnings(stdio)
+        if rf_warnings:
+            self.removed_flag_warn.setText("⚠  " + "\n".join(rf_warnings))
+            self.removed_flag_warn.show()
+            # Only offer the button when something is actually auto-migratable.
+            migrated, _ = core.migrate_removed_flags(stdio)
+            self.removed_flag_fix_btn.setVisible(migrated is not stdio)
+        else:
+            self.removed_flag_warn.hide()
+            self.removed_flag_fix_btn.hide()
 
     def _fix_args(self):
         if self._before_change:
@@ -758,6 +792,19 @@ class ServerEditor(QFrame):
         fixed, _ = core.split_suspicious_args(self._current_arg_lines())
         self.args.setPlainText("\n".join(fixed))  # triggers _emit -> recheck
 
+    def _fix_removed_flags(self):
+        if self._before_change:
+            self._before_change()
+        stdio = {
+            "command": self.command.text().strip(),
+            "args": self._current_arg_lines(),
+            "env": self.env.dump(),
+        }
+        migrated, _ = core.migrate_removed_flags(stdio)
+        # Reload env first, then args; setting args text triggers _emit -> recheck.
+        self.env.load(migrated.get("env", {}))
+        self.args.setPlainText("\n".join(migrated.get("args", [])))
+
     # --- dependency ------------------------------------------------------ #
     def refresh_dependency(self, auto_open=False):
         if not self.isEnabled():
@@ -2633,6 +2680,8 @@ class MainWindow(QMainWindow):
         for entry in self.servers:
             for warning in core.env_ref_warnings(entry.data, self.current_profile):
                 lint_warnings.append(f"'{entry.name}': {warning}")
+            for warning in core.removed_flag_warnings(entry.data):
+                lint_warnings.append(f"'{entry.name}': {warning}")
         if lint_warnings:
             self.validation_lbl.setText(f"⚠ {lint_warnings[0]}")
             self.validation_lbl.setStyleSheet(f"color: {WARN};")