feat: flatten opportunity commands, add config management, fix completions

- Flatten opportunity into top-level portfolio and opportunity commands
- Add interactive config get/set/key/secret with type coercion
- Rewrite --doc to show TUI vs JSON schema per command
- Unify agent mode output to JSON only
- Make init prompt for API key/secret interactively
- Fix coin tab completion alias binding
- Fix set_config_value reading from wrong path
- Fail loudly on invalid numeric config values

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/coinhunter/config.py

@@ -13,6 +13,11 @@ try:
 except ModuleNotFoundError:  # pragma: no cover
     import tomli as tomllib
 
+try:
+    import tomli_w
+except ModuleNotFoundError:  # pragma: no cover
+    tomli_w = None  # type: ignore[assignment]
+
 
 DEFAULT_CONFIG = """[runtime]
 timezone = "Asia/Shanghai"
@@ -128,3 +133,72 @@ def resolve_log_dir(config: dict[str, Any], paths: RuntimePaths | None = None) -
     raw = config.get("runtime", {}).get("log_dir", "logs")
     value = Path(raw).expanduser()
     return value if value.is_absolute() else paths.root / value
+
+
+def get_config_value(config: dict[str, Any], key_path: str) -> Any:
+    keys = key_path.split(".")
+    node = config
+    for key in keys:
+        if not isinstance(node, dict) or key not in node:
+            return None
+        node = node[key]
+    return node
+
+
+def set_config_value(config_file: Path, key_path: str, value: Any) -> None:
+    if tomli_w is None:
+        raise RuntimeError("tomli-w is not installed. Run `pip install tomli-w`.")
+    if not config_file.exists():
+        raise RuntimeError(f"Config file not found: {config_file}")
+    config = tomllib.loads(config_file.read_text(encoding="utf-8"))
+    keys = key_path.split(".")
+    node = config
+    for key in keys[:-1]:
+        if key not in node:
+            node[key] = {}
+        node = node[key]
+
+    # Coerce type from existing value when possible
+    existing = node.get(keys[-1])
+    if isinstance(existing, bool) and isinstance(value, str):
+        value = value.lower() in ("true", "1", "yes", "on")
+    elif isinstance(existing, (int, float)) and isinstance(value, str):
+        try:
+            value = type(existing)(value)
+        except (ValueError, TypeError) as exc:
+            raise RuntimeError(
+                f"Cannot set {key_path} to {value!r}: expected {type(existing).__name__}, got {value!r}"
+            ) from exc
+    elif isinstance(existing, list) and isinstance(value, str):
+        value = [item.strip() for item in value.split(",") if item.strip()]
+
+    node[keys[-1]] = value
+    config_file.write_text(tomli_w.dumps(config), encoding="utf-8")
+
+
+def get_env_value(paths: RuntimePaths | None = None, key: str = "") -> str:
+    paths = paths or get_runtime_paths()
+    if not paths.env_file.exists():
+        return ""
+    env_data = load_env_file(paths)
+    return env_data.get(key, "")
+
+
+def set_env_value(paths: RuntimePaths | None = None, key: str = "", value: str = "") -> None:
+    paths = paths or get_runtime_paths()
+    if not paths.env_file.exists():
+        raise RuntimeError(f"Env file not found: {paths.env_file}. Run `coin init` first.")
+
+    lines = paths.env_file.read_text(encoding="utf-8").splitlines()
+    found = False
+    for i, line in enumerate(lines):
+        stripped = line.strip()
+        if stripped.startswith(f"{key}=") or stripped.startswith(f"{key} ="):
+            lines[i] = f"{key}={value}"
+            found = True
+            break
+    if not found:
+        lines.append(f"{key}={value}")
+
+    paths.env_file.write_text("\n".join(lines) + "\n", encoding="utf-8")
+    os.environ[key] = value