* feat(web): show session branch row for local changed files
The pre-PR branch row above the composer only appeared once the branch
was pushed and ahead of the default branch. Sessions with local work
(committed, uncommitted, or untracked changes) showed nothing.
The gateway now emits the branch payload whenever the working tree has
changed files vs the default-branch merge base; createUrl is withheld
until GitHub's pull/new page has something to compare, and the UI only
renders the Create PR link when it is present.
* refactor(gateway): keep control-ui-session-prs under LOC ratchet
* docs(gateway): note explicit-base diff counts conflict paths
00b38ebc20
