Summary

This PR delivers the v2 core policy-runtime hardening for InteractiveDocumentWithTools.

Changes:

• fixes malformed-policy handling contract:
  • observe mode fails open (tool executes, logs tool_policy_error_observed)
  • enforce mode fails closed (tool blocked, logs tool_policy_error_enforced)
• refactors policy runtime into explicit helpers for readability and maintenance:
  • _evaluate_policy_decision
  • _coerce_policy_decision
  • _apply_policy_decision
  • _policy_error_outcome
• adds robust coercion for malformed PolicyDecision fields (including invalid tags shape)
• keeps default behavior unchanged when no policy is configured

Why

The previous implementation could incorrectly block tool execution in observe mode for malformed policy output. This PR makes failure semantics explicit and deterministic.

Test Coverage

• malformed policy return object
• malformed action
• malformed tags payload
• policy exceptions
• observe/enforce behavior checks
• existing tool-runtime behavior regression checks

Validation

Executed locally:

• . .venv/bin/activate && python -m pytest -q concordia/document/interactive_document_tools_test.py
• . .venv/bin/activate && python -m pytest -q concordia/document/tool_policy_test.py
• . .venv/bin/activate && python -m pytest -q concordia/document
• . .venv/bin/activate && python -m pylint --errors-only on touched files