[codex] Deepen QA test architecture

[trek-e]

Summary

• add a Foundry Import State Ledger module and focused state-file tests for missing, malformed, legacy, import-save, and projection-save cases
• route Foundry import/projection state handling through the ledger and document the new module in CONTEXT.md
• strengthen QA-oriented tests across Discord rendering, shared client calls, provider fallback, registration retry behavior, output scanning, and task scheduling
• fix suppressed Discord rendered responses so they no-op instead of sending the sentinel dict

Validation

• uv run ruff check CONTEXT.md interfaces/discord/response_renderer.py interfaces/discord/tests/test_response_renderer.py modules/pathfinder/app/foundry_import_state_ledger.py modules/pathfinder/app/foundry_chat_import.py modules/pathfinder/app/foundry_memory_projection.py modules/pathfinder/tests/test_foundry_import_state_ledger.py modules/pathfinder/tests/test_registration.py sentinel-core/tests/test_output_scanner.py sentinel-core/tests/test_provider_router.py sentinel-core/tests/test_task_runner.py shared/tests/test_sentinel_client.py
• cd modules/pathfinder && uv run pytest
• cd interfaces/discord && uv run pytest
• cd sentinel-core && uv run pytest
• cd shared && uv run pytest
• cd sentinel-core && uv run pytest ../interfaces/imessage/tests

Notes

• no uv.lock files changed