feat: enhance table layout and interaction across various components

- Introduced a new `WorkspaceTable` component for consistent table styling and behavior.
- Updated `BacktestPage`, `DatasetPage`, and `DataPreparationPage` to utilize the new `WorkspaceTable`.
- Implemented compact row heights and ellipsis for long text in table cells.
- Added validation for online field queries to ensure at least one filter is provided.
- Enhanced error handling and user feedback for invalid input scenarios.
- Improved pagination controls with dynamic page size options.
- Documented table display specifications in `ui-tables.md`.
- Added tests to verify table layout, interaction, and error handling.

backend/app/backtests/contracts.py

@@ -4,7 +4,7 @@ import hashlib
 import json
 from typing import Literal
 
-from pydantic import Field, field_validator, model_validator
+from pydantic import ConfigDict, Field, field_validator, model_validator
 
 from ..preparations.contracts import PreparationReference
 from ..schemas import Contract
@@ -56,6 +56,15 @@ class Source(Contract):
     hypothesis: str | None = Field(default=None, max_length=2000)
 
 
+class SourceOutput(Source):
+    """Project stored metadata onto the public source fields; input remains strict.
+
+    Removed or internal keys are never returned or converted to snapshot references.
+    Known fields still undergo normal validation.
+    """
+
+    model_config = ConfigDict(extra="ignore")
+
 
 
 class DraftInput(Contract):
@@ -145,7 +154,7 @@ class PreviewOutput(Contract):
     preview_id: str
     version: int
     name: str
-    source: Source
+    source: SourceOutput
     digest: str
     total: int
     batch_count: int
@@ -163,7 +172,7 @@ class RunOutput(Contract):
     backtest_run_id: str
     preview_id: str
     name: str
-    source: Source
+    source: SourceOutput
     ai_context: dict
     control: Literal["active", "paused", "stopped"]
     status: str