[Relax] Fix llama4_rope_with_position_map to support partial rotary factor

[guan404ming]

Related Issue

closes #17715

Why

• Phi-4 uses: partial_rotary_factor = 0.75 (rotary_dim = 96) + longrope scaling
• Longrope requires: Both long_factors + short_factors packed into one buffer
• Expected buffer size: (rotary_dim,) = (96,) total
  • First half [0:48] = long_factors
  • Second half [48:96] = short_factors
• llama4_rope_with_position_map still had old size (rotary_dim // 2,) = (48,)

[guan404ming]

cc @tlopex @mshr-h

[tlopex]

cc @MasterJH5574