Stage 5 (SummarySynthesizer) was only sending aggregate timeline stats to the
LLM (cluster count, burst count, gap count) — the actual sequenced cluster data
that Stage 1 reconstructed was never included. The LLM had no per-cluster
timestamps, severity, burst flags, silence gaps, or representative text to
write the TIMELINE section from.
Added _build_timeline_block() to emit a numbered per-cluster summary matching
the format Stage 3 uses for the hypothesizer, and included it in the user
message alongside the hypothesis block.
Also fixed _build_hypothesis_block() to include the 2-4 sentence description
each hypothesis carries — previously only the title and novelty score reached
the LLM.
11 new tests cover _build_timeline_block() directly (burst label, gap threshold,
pattern tags, text truncation at 200 chars, null start_iso, multi-cluster
numbering). 529 tests passing.