Implement BotResetLastAvoidReach and export it via botlib API

[themuffinator]

Motivation

• Restore Quake III parity for handling the most-recent avoided reachability by tracking/resetting it separately from the full avoid list as described in docs/be_ai_parity_matrix.md.
• Provide a small, focused API to clear only the latest avoid timer so movement/pathfinding can recover without clearing all avoid state.

Description

• Implemented BotResetLastAvoidReach in src/botlib/ai_move/bot_move.c with the required commented header and logic that clears the most recently-timed entry and decrements its try counter if set.
• Added the declaration void BotResetLastAvoidReach(int movestate); to src/botlib/ai_move/bot_move.h so the function is exported from the move module.
• Exposed the helper through the botlib interface by adding BotInterface_BotResetLastAvoidReach in src/botlib/interface/bot_interface.c and wiring it into the export table as BotResetLastAvoidReach.
• Updated the bridge/export header src/q2bridge/botlib.h to include the new function pointer in the bot_export_t structure.

Testing

• No automated tests were run for this change.

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Codex Task