fix(get_path): bump default max_attempts + env-var override

[rasdani]

GetPath.call polls the async path-handle with exponential backoff (50ms → 1s cap). The old 10-attempt default gave ~6.5s wall-clock budget, which is not enough on a fresh world: the first distant move_to has to wait for Factorio's chunk-generation before A* can even start, and chunk-gen routinely exceeds 6.5s.

Empirically:

• 24-task gpt-5.4 throughput eval at the 10-attempt default: 12/129 tool messages (~9.3%) raised "Path request timed out after 10 attempts", always on the first distant move_to of each rollout.
• 6-task Sonnet-4.5 eval at a 30-attempt client-side patch: 2/229 (~0.9%).
• 1-task gpt-4o eval at 60-attempt: 1/40 (~2.5%).

Bumping the default to 120 (~115s wall-clock budget). Override with FLE_GETPATH_MAX_ATTEMPTS=N when running on slower hardware, or lower it explicitly if failing fast on unreachable targets matters more than tolerating cold chunks.