Zero token counts for empty transcripts and README alignment

[gistrec]

Motivation

• Avoid counting tokens for the user-facing fallback text when transcription is empty and ensure zero token counts are recorded for empty transcriptions.
• Keep stored text user-friendly while basing token accounting on the raw recognition output.
• Fix README schema formatting so the llm_tokens_by_model column aligns with other columns for readability.

Description

• Update utils/tokens.py so tokens_by_model returns zeros for every model when text.strip() is empty and keep LLM_TOKEN_MODELS-based mapping.
• Change schedulers/transcription.py to compute token_counts = tokens_by_model(raw_text) using the raw parse_text(result) output and then replace empty text with the friendly fallback string before persisting results.
• Persist llm_tokens_by_model=token_counts on both successful and failed updates in update_transcription calls.
• Adjust README.md spacing for the llm_tokens_by_model JSON column to align with other schema columns.

Testing

• No automated tests were run for this change.
• Local static inspection and manual review of modified files were performed during the rollout and changes were committed successfully.

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Codex Task