Handle existing OpenCode JSONC defaults (#1867)

Follow-up to #1866 addressing both Cubic findings before release:

- recognize schema-only OpenCode JSONC with comments and trailing commas
- exercise the intended preservation branch with valid JSON
- also verify administrator-selected JSONC remains byte-for-byte
unchanged

Verification: focused config tests pass (5 passed).

<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Fixes detection of schema-only OpenCode JSONC configs so comments,
trailing commas, and escaped keys no longer prevent the default model
from being added.

- Replaces strict JSON parsing with a JSONC-aware parser that strips
comments and trailing commas before checking whether a config only sets
`$schema`.
- Writes the default config as JSONC text instead of JSON.
- Expands tests to cover plain JSON, JSONC with comments and trailing
commas, and escaped schema keys.

<sup>Written for commit c1358a2726298e20db1a8697647338baa21e555f.
Summary will update on new commits.</sup>

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archivebox/opencode/views.py

@@ -2,7 +2,6 @@ from __future__ import annotations
 
 import atexit
 import base64
-import json
 import logging
 import os
 import re
@@ -43,6 +42,11 @@ _PROXY_PREFIX_REGEX = _PROXY_PREFIX.replace("/", r"\/")
 _PROXY_PREFIX_NO_SLASH_REGEX = _PROXY_PREFIX.lstrip("/").replace("/", r"\/")
 _CONFIG_PATH = Path(opencode_plugin.__file__).with_name("config.json")
 _DEFAULT_MODEL = "opencode/big-pickle"
+_DEFAULT_CONFIG = f'''{{
+  "$schema": "https://opencode.ai/config.json",
+  "model": "{_DEFAULT_MODEL}"
+}}
+'''
 
 _TEXT_CONTENT_TYPES = (
     "text/",
@@ -323,19 +327,8 @@ def _ensure_project_files(settings: dict) -> None:
         opencode_skill_path.symlink_to(editable_skill_path)
 
     opencode_config_path = settings["config_home"] / "opencode" / "opencode.jsonc"
-    default_config = {
-        "$schema": "https://opencode.ai/config.json",
-        "model": _DEFAULT_MODEL,
-    }
     if not opencode_config_path.exists():
-        opencode_config_path.write_text(f"{json.dumps(default_config, indent=2)}\n")
-    else:
-        try:
-            existing_config = json.loads(opencode_config_path.read_text())
-        except (OSError, ValueError):
-            existing_config = None
-        if isinstance(existing_config, dict) and set(existing_config) <= {"$schema"}:
-            opencode_config_path.write_text(f"{json.dumps(default_config, indent=2)}\n")
+        opencode_config_path.write_text(_DEFAULT_CONFIG)
 
 
 def _ensure_default_session(settings: dict) -> str:

archivebox/tests/test_opencode_agent.py

@@ -445,13 +445,20 @@ def test_opencode_state_dir_is_separate_from_workdir(tmp_path):
     assert json.loads((state_dir / "config" / "opencode" / "opencode.jsonc").read_text())["model"] == "opencode/big-pickle"
 
 
-def test_opencode_preserves_existing_config(tmp_path):
+@pytest.mark.parametrize(
+    "existing_config",
+    [
+        '{"model": "anthropic/claude-sonnet-4-5"}\n',
+        '{\n  // Keep the administrator-selected model.\n  "model": "anthropic/claude-sonnet-4-5",\n}\n',
+        '{\n  // Schema-only files are still user-owned.\n  "$schema": "https://opencode.ai/config.json",\n}\n',
+    ],
+)
+def test_opencode_preserves_existing_config(tmp_path, existing_config):
     from archivebox.opencode import views
 
     state_dir = tmp_path / "state"
     config_path = state_dir / "config" / "opencode" / "opencode.jsonc"
     config_path.parent.mkdir(parents=True)
-    existing_config = '{\n  // Keep the administrator-selected model.\n  "model": "anthropic/claude-sonnet-4-5"\n}\n'
     config_path.write_text(existing_config)
 
     views._ensure_project_files(
@@ -466,26 +473,6 @@ def test_opencode_preserves_existing_config(tmp_path):
     assert config_path.read_text() == existing_config
 
 
-def test_opencode_adds_default_model_to_schema_only_config(tmp_path):
-    from archivebox.opencode import views
-
-    state_dir = tmp_path / "state"
-    config_path = state_dir / "config" / "opencode" / "opencode.jsonc"
-    config_path.parent.mkdir(parents=True)
-    config_path.write_text('{"$schema": "https://opencode.ai/config.json"}\n')
-
-    views._ensure_project_files(
-        views._settings(
-            {
-                "OPENCODE_WORKDIR": str(tmp_path / "workdir"),
-                "OPENCODE_STATE_DIR": str(state_dir),
-            },
-        ),
-    )
-
-    assert json.loads(config_path.read_text())["model"] == "opencode/big-pickle"
-
-
 def test_opencode_defaults_to_the_archivebox_collection():
     from archivebox.opencode import views