Expand parity harness coverage before behavioral drift lands

The landed mock Anthropic harness now covers multi-tool turns, bash flows,
permission prompt approve/deny paths, and an external plugin tool path.
A machine-readable scenario manifest plus a diff/checklist runner keep the
new scenarios tied back to PARITY.md so future additions stay honest.

Constraint: Must build on the deterministic mock service and clean-environment CLI harness
Rejected: Add an MCP tool scenario now | current MCP tool surface is still stubbed, so plugin coverage is the real executable path
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Keep rust/mock_parity_scenarios.json, mock_parity_harness.rs, and PARITY.md refs in lockstep
Tested: cargo fmt --all
Tested: cargo clippy --workspace --all-targets -- -D warnings
Tested: cargo test --workspace
Tested: python3 rust/scripts/run_mock_parity_diff.py
Not-tested: Real MCP lifecycle handshakes; remote plugin marketplace install flows

rust/README.md

@@ -56,12 +56,19 @@ Harness coverage:
 - `grep_chunk_assembly`
 - `write_file_allowed`
 - `write_file_denied`
+- `multi_tool_turn_roundtrip`
+- `bash_stdout_roundtrip`
+- `bash_permission_prompt_approved`
+- `bash_permission_prompt_denied`
+- `plugin_tool_roundtrip`
 
 Primary artifacts:
 
 - `crates/mock-anthropic-service/` — reusable mock Anthropic-compatible service
 - `crates/rusty-claude-cli/tests/mock_parity_harness.rs` — clean-env CLI harness
 - `scripts/run_mock_parity_harness.sh` — reproducible wrapper
+- `scripts/run_mock_parity_diff.py` — scenario checklist + PARITY mapping runner
+- `mock_parity_scenarios.json` — scenario-to-PARITY manifest
 
 ## Features