Purpose: the CBAM timeline as a single ordered view - from the founding regulation through the transitional period to the definitive regime and the surrender phase. Guidelines: call this first whenever a question involves CBAM dates, obligations or scope ("when does CBAM start", "when must certificates be surrendered"). Grouped into transitional/legislative, definitive and surrender phases by the as-of date of each source document. Limits: timeline only - dates come from the cited official documents and are not forecasts; the phase grouping is ours, not the EU's official staging. Pair with get_domain_benchmark(id=...) for the source URL of any node. Ex: get_cbam_timeline(), get_cbam_timeline(language='en').