Builds the system prompt for dynamic form extraction.
Uses a mandatory scratchpad → JSON two-step approach optimised for GPT-4o.
Three-tier evidence classification (STATED / INFERABLE / UNCERTAIN) enforces
a hard confidence gate. A verification pass after per-field reasoning catches
any silently skipped fields before the JSON commit.
Builds the system prompt for dynamic form extraction.
Uses a mandatory scratchpad → JSON two-step approach optimised for GPT-4o. Three-tier evidence classification (STATED / INFERABLE / UNCERTAIN) enforces a hard confidence gate. A verification pass after per-field reasoning catches any silently skipped fields before the JSON commit.