interactive/changes.md carries an orphaned diff3 conflict marker (||||||| 84a19a642) on main

## What

`packages/coding-agent/src/modes/interactive/changes.md` line 73 on `main` (@ b3b073af4) contains an orphaned diff3 conflict-marker base separator:

```
||||||| 84a19a642
```

There is no matching `<<<<<<<` / `=======` / `>>>>>>>` — a merge resolution committed the base marker line as content. It sits between the "Explain disk-capacity failures during uncaught interactive shutdown (2026-08-29)" entry and its neighbors.

## Why it matters

- This tracker is parsed by the changelog gate (`scripts/changes-md-policy.mjs` `parseTrackerEntries`); stray marker lines can silently distort entry blocks or coverage attribution for future PRs.
- Next upstream sync tooling that greps for conflict markers will flag this file.

## Fix

Delete line 73 (one-line docs change; `no-changelog` label applies).

Found during the 2026-08-29 #1174 work (PR #1187 touched the same tracker).

Open packages/coding-agent/src/modes/interactive/changes.md at line 73 and confirm the orphaned diff3 base marker between the named tracker entry and its neighbors. Remove that one line, then run the changelog gate in scripts/changes-md-policy.mjs to verify the tracker still parses without conflict-marker or coverage issues.

Written by the indexing model from the issue text.