Improve stat-cache-hitrate UX and normalize Total Running metric

[mouxinqq]

Motivation

• Make the stat-cache-hitrate skill output easier to read and align total_running with the prefill worker semantics.
• Avoid documenting an explicit Other option in the skill prompt because the client provides that input automatically.
• Produce session details in a horizontally scrollable single-line format to avoid wide Markdown table wrapping.

Description

• Updated the skill guidance in SKILL.md to keep two fixed log-path options and remove the explicit Other entry, relying on the client-supplied Other input.
• Normalized the per-window total_running value by dividing stats.total_running by 2 and added _format_half_running to format integer/decimal results; the window column is renamed to Total Running (prefill≈stats/2).
• Replaced the wide Markdown session detail table with a single-line TSV export rendered by _render_scrollable_tsv so each session is one TSV line for horizontal scrolling.
• Propagated the running-column name change into window_utils.merge_blank_window_rows via a RUNNING_COL constant so merged window output preserves the renamed running field.

Testing

• Ran python3 -m py_compile on the updated scripts (stat_cache_hitrate.py, window_utils.py, session_analysis.py, chart.py, log_parser.py) and compilation completed without errors.
• Manual inspection ensured SKILL.md text reflects the new prompt and session detail format and that report generation points to details/session_hit_details.md using the TSV block format.

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Codex Task