Adds `columnDwellMs?: Record<string, number>` to Task — a per-column
accumulator (column name -> cumulative ms) recorded at the same store
column-transition seam as `cumulativeActiveMs`. On every move it adds
`columnMovedAt(new) - columnMovedAt(prev)` to the bucket for the column
being left, clamped >= 0; unparseable/missing prior timestamps and 0-dwell
moves are skipped, and second visits add to the existing bucket.
Motivation: `cumulativeActiveMs` only measures in-progress time. Diagnosis
of slow tasks showed the dominant wall-clock is *waiting* (queue time in
todo, review wait in in-review), which previously had to be reconstructed
from agent logs. This makes per-stage dwell directly queryable, like
productivity-analytics already consumes cumulativeActiveMs.
Persisted as a JSON-text task column following the v129 workspaceWorktrees
precedent: SCHEMA_SQL column + SCHEMA_VERSION 129->130 + versioned
addColumnIfMissing migration. Additive and behavior-preserving; pre-existing
rows start NULL and accumulate from their next transition. Survives
archive/restore. @fusion/core is private — no changeset.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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