Add per-raw-hit calibration fields, separate clean offset, and update TDC bin comment

[wooyeonkwon]

Motivation

• Preserve and expose per-raw-hit calibration so downstream code can access the channel Gaussian mean and a calibrated raw time for every hit.
• Keep the clean-hit offset separate from the per-raw-hit stored offset and reflect the updated TDC binning policy in the header comment.

Description

• Added offset and tdc_cali_raw vectors to EventBuffers and created corresponding output branches offset and tdc_cali_raw to store per-raw-hit Gaussian mean and calibrated raw time (computed as rec.tdc - offset).
• Renamed the previously shared offset vector for clean hits to offset_clean to avoid reusing the same container for raw and clean values, and created the offset_clean branch.
• Moved computation of the per-hit offset and tdc_cali_raw earlier so every raw hit gets a stored calibration value regardless of clean selection, and retained the clean-selection logic that fills ch, tdc, and clean_rawIndex using offset_clean.
• Updated header comment to reflect the TDC raw binning change from 1000 to 20000 units and adjusted bounds checks for channel mapping against calibration.offsets.

Testing

• Built the binary with g++ -O2 -std=c++17 main_mRPC.cc \\root-config --cflags --libs`` and the build completed successfully.
• Ran the repacker on a representative test input and verified the output ROOT Events tree contains the new offset, tdc_cali_raw, and offset_clean branches and that execution completed without errors.

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Codex Task