feat: share one drift classifier across sync/update/change/CI (#884)

[prompt-driven-github]

Summary

Introduces a shared, pure drift classifier (pdd/drift_classifier.py, defined by a new prompt) and wires the five existing artifact-drift classification paths to build a common DriftInputs and consume a structured DriftVerdict. Repair plans remain command-specific in this first PR — only the classification step is unified.

Closes #884

Changes Made

Prompts Created

• pdd/prompts/drift_classifier_python.prompt — new pure classifier prompt; Pydantic v2 DriftInputs / DriftVerdict, enumerated DriftReason, git diff as an explicit input field (not a CI-only correction).

Prompts Modified

• pdd/prompts/sync_determine_operation_python.prompt — builds DriftInputs, calls classify_drift, maps verdict onto the existing fingerprint state machine.
• pdd/prompts/update_main_python.prompt — pdd update --all path now constructs DriftInputs (including git_change_set) and calls the shared classifier.
• pdd/prompts/ci_drift_heal_python.prompt — CI auto-heal passes its git diff in as git_change_set; drops the post-hoc reclassification branch.
• pdd/prompts/agentic_change_orchestrator_python.prompt — pdd change preflight calls classify_drift to decide whether to heal.
• pdd/prompts/sync_main_python.prompt — no-arg pdd sync Tier 1 global scan classifies each module through the shared classifier.

Documentation Created

• docs/drift_classifier.md — design doc / module-level API sketch (satisfies acceptance criterion pdd install_completion: install_completion() got unexpected keyword argument 'quiet' #1).

Other

• architecture.json — registers the new drift_classifier module.

Review Checklist

• Prompt syntax is valid
• PDD conventions followed
• Documentation is up to date
• Characterization tests cover sync_determine_operation, CI auto-heal, and change preflight (per acceptance criterion Claude-3-5-Haiku outputting code in structured json format #4)

Next Steps After Merge

1. Regenerate code from modified prompts in dependency order:

   ./sync_order.sh

   Or manually:

   pdd sync drift_classifier
   pdd sync agentic_change
   pdd sync agentic_change_orchestrator
   pdd sync agentic_sync_runner
   pdd sync one_session_sync
   pdd sync operation_log
   pdd sync sync_determine_operation
   pdd sync durable_sync_runner
   pdd sync prompts
   pdd sync sync_main
   pdd sync agentic_sync
   pdd sync checkup
   pdd sync checkup_review_loop
   pdd sync ci_drift_heal
   pdd sync maintenance
   pdd sync update_main
   pdd sync agentic_checkup
   pdd sync modify
   pdd sync pin_example_hack
   pdd sync sync_orchestration
   

2. Run tests to verify functionality (characterization fixtures should preserve current verdicts for the three required paths).
3. Deploy if applicable.

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Created by pdd change workflow

[greptile-apps]

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