chore: clean up stranded .server-changes/ files from v4.4.5 (#3509)

## Summary

Delete 34 `.server-changes/*.md` files that should have been cleaned up
automatically when v4.4.5 (#3406) was merged but were stranded by a
workflow race.

## Why these are stale

The `update-lockfile` job in `.github/workflows/changesets-pr.yml` is
what cleans up consumed `.server-changes/*.md` files on the release
branch. When v4.4.5 was merged on 2026-05-01, the post-merge workflow
run on `main` failed at `pnpm install --frozen-lockfile` (stale lockfile
in the merge commit), and `cancel-in-progress: true` cancelled the
in-flight run from the previous push — so `update-lockfile` never
reached the cleanup step.

Result: the 34 files described changes that v4.4.5 already shipped, and
they were re-appearing in the v4.4.6 release PR (#3501) under "Server
changes" plus showing up as deletions in its diff.

## What this PR keeps

- `fix-rollback-schedule-sync.md` — genuinely new for v4.4.6 (#3468),
the only server change introduced after v4.4.5
- `README.md`, `.gitkeep` — directory infrastructure
- `dev-cli-disconnect-md` — leaving alone (typo'd filename from March,
no `.md` extension, not picked up by the cleanup glob anyway)

## After merge

The next run of `changesets-pr.yml` will refresh #3501 with a "Server
changes" section that only lists the v4.4.6 entry, and the only
`.server-changes/` deletion in its diff will be
`fix-rollback-schedule-sync.md`.

## Related

- #3505 is the proper underlying fix — collapses the three-job graph
into a single atomic commit by `changesets/action` so this race can't
strand the cleanup again. This PR is just the one-time catch-up for the
files that already got stranded.

Author: ericallam