Edit-tool results carried the full pre/post file content in
`details.oldText` / `details.newText`. For large files this bloated each
per-turn JSONL line by hundreds of KB even though the snapshots are
never sent to the LLM (provider serializers send only `content`) and
only consumed by the ACP event mapper for diff visualization.
Add `pruneOversizedEditSnapshots` and apply it at every site that
constructs an `EditToolDetails` / `EditToolPerFileResult`:
`executePatchSingle`, `executeReplaceSingle`, hashline `renderSection`
(delete + update branches), and both aggregators in `edit/index.ts`.
When combined `oldText` + `newText` exceeds 32 KB the helper returns a
shallow copy with both fields omitted; smaller edits pass through
unchanged. The diff, path, firstChangedLine, op, move, and diagnostics
fields are preserved, and ACP returns no diff content for over-budget
files (the text content still flows — graceful degradation).
Fixes#3786
roboomp
9e4e0f6691