Implement and export BotResetLastAvoidReach

[themuffinator]

Motivation

• Restore the missing movement helper flagged in the parity matrix by implementing the retail BotResetLastAvoidReach behavior.
• Ensure avoid-reach bookkeeping can be reset per-retail semantics so navigation and avoidance heuristics behave correctly.
• Expose the helper through the botlib interface so the game/engine can call the same API as the original DLL.

Description

• Added BotResetLastAvoidReach implementation in src/botlib/ai_move/bot_move.c with the required commented header and retail-style logic to clear the most recent avoid reach entry.
• Declared the prototype in src/botlib/ai_move/bot_move.h.
• Added a bridge shim BotInterface_BotResetLastAvoidReach in src/botlib/interface/bot_interface.c and wired it into the export table as BotResetLastAvoidReach.
• Updated src/q2bridge/botlib.h to include the BotResetLastAvoidReach function pointer in the exported API structure.

Testing

• No automated tests or CI jobs were executed for this change.

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Codex Task