v1.6.1

Whole-file writes no longer break the diff cards

Harness 0.1.5 records meta.diffs: [] for a file a write call creates, so the card falls back to the argument-derived whole-file hunk — whose oldText was null there. The card's cache key read null.length and crashed; one crash abdicated the slot entry, and every further edit/write call silently fell back to the stock collapsed row. That is the "inline diff is broken in the new harness" report.

Argument-derived hunks now carry oldText: "" (the same normalization wire hunks already get). An empty old side diffs as all-added, which is the intended whole-file view — created files show a fully green right column with real gutter numbers again. Ships with a regression test for the exact crash shape.