feat(datafabric): add choice-set awareness to NL-to-SQL pipeline

[UIPath-Harshit]

Summary

• Adds choice-set field awareness across the NL-to-SQL pipeline — from schema resolution through prompt generation to result post-processing
• Resolves DS-8647: Handle queries involving choice sets

Problem

The NL-to-SQL pipeline had zero choice-set awareness. Choice-set fields (CHOICE_SET_SINGLE / CHOICE_SET_MULTIPLE) were rendered as raw SQL types (int / nvarchar) with:

• No value metadata (LLM had no idea Critical=0, High=1, etc.)
• No label-to-NumberId mapping in prompts
• No choice-set-specific SQL patterns in constraints
• No result post-processing to translate NumberIds back to labels
• No cross-entity shared choice-set join hints

This caused incorrect SQL generation (e.g. WHERE Priority = 4 instead of Priority = 0 for "Critical") and unintelligible results ("priority 0" instead of "Critical").

Changes

File	What
models.py	ChoiceSetValueSchema, choiceset_id/choiceset_values on FieldSchema, is_choice_set property, is_numeric returns False for CS fields, shared_choicesets/choiceset_label_maps on SQLContext
datafabric_prompt_builder.py	Fetch CS values via SDK during schema resolution, bridge choiceSetId alias mismatch via entity GET, render value mappings inline + dedicated section, emit cross-entity shared CS join hints
datafabric_subgraph.py	QueryExecutor enriches results with _label suffix columns for CS NumberIds
datafabric_prompts.py	Rule 12: "Choice-set fields use integer NumberIds"
prompts/v1.py	CHOICE-SET FIELDS section in VALUE RESOLUTION step, EMPTY_RESULT recovery references CS mappings

Test plan

• 117 existing unit tests pass with zero regressions
• 15/15 comprehensive gap verification tests pass (8 deterministic SDK/prompt/model + 7 live NL-to-SQL agent queries)
• Tested against 3 live entities on alpha: SupportTickets (3 CS fields), TicketComments (shared CS + FK), AgentShifts (shared CS, no FK)
• Run full BIRD eval suite to confirm no regression on non-CS queries

10 Gaps Addressed

Gap	Before	After
1: CS value in WHERE	Priority = 4 (wrong)	Priority = 0 (correct)
2: FieldSchema model	No CS awareness	is_choice_set, values, mapping_str
3: Label→NumberId	No mapping in prompt	Critical=0, High=1... inline
4: SQL constraints	Zero CS mentions	Rule 12 added
5: Query patterns	String quotes on INT	CS filter pattern with NumberId
6: Result labels	"priority 0"	Priority_label: 'Critical'
7: Cross-entity CS	Worked by accident	Semantic + labels
8: FK join + CS filter	Lucky guess	Consistent correct IDs
9: Explicit string join	Already worked	No regression
10: Pure CS join	Refused to join	Generates LEFT JOIN with shared CS hint

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