Support custom summarize timestamp column

[stacknil]

Summary

• add --timestamp-col to the summarize CLI command
• make summarize validate and normalize custom timestamp columns consistently with run
• document the summarize inspection command and add CLI coverage for custom timestamp columns

Tests

• pytest tests/test_cli_summarize.py tests/test_cli_errors.py tests/test_io.py
• pytest
• python -m telemetry_window_demo.cli run --config configs/default.yaml

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Point output artifact claim to the run command

After adding the summarize examples, the sentence “That command reads data/raw/sample_events.jsonl and regenerates:” now follows the summarize bullets, but summarize only prints stats and does not write features.csv, alerts.csv, or plots. This README flow now misstates actual CLI behavior and can mislead users reproducing outputs; the sentence should explicitly reference python -m telemetry_window_demo.cli run --config configs/default.yaml (or be moved back under that command).

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