refactor: Search pipeline run refactoring and baseline unit tests

[yuechao-qin]

TL;DR

Refactored the list method in PipelineRunsApiService_Sql to improve code organization and added comprehensive test coverage for pipeline run operations.

What changed?

Functional

None.

Other

• Extracted filter parsing logic into separate helper functions _resolve_filter_value and _build_filter_where_clauses
• Moved pipeline run response creation logic into a dedicated _create_pipeline_run_response method
• Added constants _PAGE_TOKEN_OFFSET_KEY and _PAGE_TOKEN_FILTER_KEY for page token field names
• Added comprehensive test suite covering listing, filtering, pagination, annotation CRUD operations, and helper functions

How to test?

uv run pytest tests/test_api_server_sql.py

Run the new test suite in tests/test_api_server_sql.py which includes:

• Tests for listing pipeline runs with various filters and pagination
• Tests for pipeline name resolution and execution stats inclusion
• Tests for annotation management (set, delete, list)
• Tests for filter parsing and page token handling
• Edge cases like empty results and unsupported filters

Why make this change?

1. Refactoring upfront — structural changes land here so upstream PR diffs only show new functionality, not mixed refactoring noise.
2. Baseline tests — establishing coverage now means each upstream PR's test additions map directly to its new features, making review clearer.

[yuechao-qin]

• feat: Add include_sql to Search Pipeline Run API #135
• feat: Search pipeline run API uses pagination cursor #131
• feat: Search within date range in pipeline run API #130
• feat: Search pipeline name in pipeline run API #129
• refactor: Convert legacy filter to be filter_query #128
• feat: Search created by user in pipeline run API #108
• feat: Search annotations in pipeline run API #107
• feat: Create Pydantic models for Search Pipeline Run API #106
• refactor: Search pipeline run refactoring and baseline unit tests #105 👈 (View in Graphite)
• master

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