feat: add meta-search client

[e06084]

No description provided.

[gemini-code-assist]

Code Review

This pull request introduces a new meta_search backend (MetaSearchClient) for Sciverse metadata search, refactoring the existing AgenticSearchClient to share common logic, and updates the CLI and configuration to support new parameters like sorting, freshness boosts, and filters. Feedback on these changes highlights a high-risk substring check in query formatting that could silently corrupt search queries, a vulnerability in filter normalization where malformed filters produce nonsense outputs, and minor code quality issues in the MetaSearchClient constructor regarding an unused parameter and unnecessary argument forwarding.

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[gemini-code-assist]

If an explicit filter is malformed (e.g., it contains "field" but is missing "value", or vice versa), it will currently fall through to the shortcut normalization loop. This treats "field" or "value" as a custom field name, producing a nonsense filter like {"field": "field", "operator": "FILTER_OP_EQ", "value": "some_field_name"}.

To prevent this, ensure that if either "field" or "value" is present in the item, it is treated as an explicit filter attempt and skipped if incomplete.

Suggested change

	if "field" in item and "value" in item:
	item = dict(item)
	item.setdefault("operator", MetaSearchClient._default_filter_operator(item))
	normalized.append(item)
	continue
	if "field" in item or "value" in item:
	if "field" in item and "value" in item:
	item = dict(item)
	item.setdefault("operator", MetaSearchClient._default_filter_operator(item))
	normalized.append(item)
	continue

[gemini-code-assist]

There are two improvement opportunities in this constructor:

1. Unused Parameter: search_type is stored as self.search_type but is never used anywhere in MetaSearchClient (e.g., in _build_public_payload or _build_local_payload). If the Sciverse meta-search API expects a search type parameter, it should be included in the payload. Otherwise, consider removing it to avoid dead code.
2. Unnecessary *args: Forwarding *args to super().__init__ is unnecessary and can be error-prone. Since search clients are typically instantiated via keyword arguments (e.g., in create_client), it is cleaner and more idiomatic to use **kwargs and forward them directly.

Suggested change

	def __init__(
	self,
	*args,
	search_type: str = "paper",
	sort_by: str | None = None,
	freshness_boost: str | None = None,
	filters: list[dict[str, Any]] | dict[str, Any] | None = None,
	**kwargs: Any,
	) -> None:
	self.search_type = search_type
	self.sort_by = sort_by
	self.freshness_boost = freshness_boost
	self.filters = self._normalize_filters(filters)
	super().__init__(*args, **kwargs)
	def __init__(
	self,
	search_type: str = "paper",
	sort_by: str | None = None,
	freshness_boost: str | None = None,
	filters: list[dict[str, Any]] | dict[str, Any] | None = None,
	**kwargs: Any,
	) -> None:
	self.search_type = search_type
	self.sort_by = sort_by
	self.freshness_boost = freshness_boost
	self.filters = self._normalize_filters(filters)
	super().__init__(**kwargs)