Fix test suite

[Randl]

This makes test suite green locally except for MCP tests.

Functional changes / bug fixes

• Fixed reset isolation: clears stale paths, corpses, orphan characters, restores resources and deterministic daytime.
• Restored public FactorioInstance.get_production_stats() and exposed pricing data.
• Fixed render centering so explicit center and player position remain distinct.
• Fixed namespace save/load, including entities, protected tools, and legacy pickles.
• Improved connect_entities validation to avoid false successful pipe connections.
• Improved placement validation/errors and updated A2A messaging compatibility.
• Added missing task definitions and task method type annotations.

Test fixes

• Added xdist worker isolation and restoration of terrain/resources between tests.
• Strengthened multi-agent tests for state round-trips, namespace isolation, shared world state, and exact messages.
• Restored the 1,000-belt load test with derived layout and a 120-second wall-time limit.
• Restored functional mining, research, profit, assembly-line, save/load, and legacy compatibility assertions.
• Removed brittle sleeps/coordinates where practical and fixed fluid-test routing order.
• Kept the unavailable public-blueprint test skipped; sprite and optional MCP tests skip when dependencies are absent.