feat: offer guided repair when loading a broken config file

If a config file on disk fails strict JSON parsing, BCC now runs it
through the same repair pipeline as pasted snippets and shows a dialog
listing the parse error, each fix it would apply, and a preview of the
resulting file. The user chooses: Repair & load (marks the profile
dirty; the file is only rewritten on Save, after the broken original
is backed up) or Cancel. Unsalvageable files keep the old error path.

repair_config_file() in bcc_core never writes to disk itself.

tests/test_json_repair.py

@@ -2,6 +2,8 @@
 parse_pasted_json_verbose). Every case here is a shape people actually paste
 from MCP docs, blog posts, and chat windows."""
 
+import json
+
 import pytest
 
 import bcc_core as c
@@ -170,6 +172,35 @@ def test_kitchen_sink():
     assert len(notes) >= 4
 
 
+# --------------------------------------------------------------------------- #
+# Config-file repair (load-time)
+# --------------------------------------------------------------------------- #
+def test_repair_config_file_fixes_and_reports(tmp_path):
+    p = tmp_path / "claude_desktop_config.json"
+    p.write_text(
+        '{\n  "globalShortcut": "Cmd+Space",\n'
+        "  // my servers\n"
+        '  "mcpServers": {\n'
+        '    "brave": {"command": "npx", "args": ["-y"],},\n'
+        "  },\n}"
+    )
+    cfg, notes, preview = c.repair_config_file(p)
+    assert cfg["mcpServers"]["brave"]["command"] == "npx"
+    assert cfg["globalShortcut"] == "Cmd+Space"  # unrelated keys survive
+    assert any("comment" in n for n in notes)
+    assert any("trailing" in n for n in notes)
+    assert json.loads(preview) == cfg
+    # nothing was written to disk
+    assert "//" in p.read_text()
+
+
+def test_repair_config_file_hopeless_raises(tmp_path):
+    p = tmp_path / "claude_desktop_config.json"
+    p.write_text("total nonsense, no braces at all")
+    with pytest.raises(ValueError):
+        c.repair_config_file(p)
+
+
 # --------------------------------------------------------------------------- #
 # Still fails cleanly on hopeless input
 # --------------------------------------------------------------------------- #