self-host-nightly.yml's filename no longer matches its manual-only, unscheduled nature

[JSONbored]

Context

.github/workflows/self-host-nightly.yml is named after a "nightly" cadence it no longer has — and,
per its own header comment, never runs unattended at all:

# Manual maintenance hook for externally reachable self-host stacks. This is deliberately not scheduled
# while the review stack is running without colocated GitHub Actions runners.
...
name: self-host maintenance

on:
  workflow_dispatch: {}

There is no schedule: trigger anywhere in the file — workflow_dispatch: {} is the only trigger, and
the comment explicitly states this is deliberate. The workflow's own name: field (self-host maintenance, what shows in the Actions UI) already reflects this correctly. Only the filename
still says self-host-nightly.yml, a holdover from before issue #4899 ("Generalize the
self-host-nightly workflow beyond a single URL", closed) generalized it to a fleet matrix and — at some
point — removed its schedule trigger; the file was never renamed to match.

This is misleading to anyone scanning .github/workflows/ by filename (the most common way to survey
a repo's automation): the name implies an unattended nightly job, when the workflow is actually a
manual-only operator hook. A repo-wide search confirms nothing else references this file by name
(grep -rln "self-host-nightly" --include="*.md" --include="*.yml" --include="*.ts" . returns only the
file itself), so renaming it is a self-contained, mechanical change with no other call sites to update.

Requirements

• Rename .github/workflows/self-host-nightly.yml to .github/workflows/self-host-maintenance.yml
  (matching the workflow's own name: field, self-host maintenance, and this repo's general
  convention of filename mirroring the name: field — see e.g. stuck-check-watchdog.yml's name: Stuck required-check watchdog, cache-cleanup.yml's name: Clean up closed-PR caches).
• Do not change the workflow's name: field, triggers, jobs, or any other content — this is a
  filename-only rename.
• Confirm no other file in the repo references the old filename before/after the rename (re-run the
  grep above post-rename to confirm it's clean).
• Note: renaming a workflow file does not affect its past Actions run history (GitHub keeps historical
  runs associated with the workflow's file path at the time each run happened) or its
  workflow_dispatch entry point (GitHub Actions resolves dispatch targets by current file path in the
  default branch) — no further migration steps are needed.

Deliverables

• .github/workflows/self-host-nightly.yml renamed to .github/workflows/self-host-maintenance.yml
  with no other changes.

Test Coverage Requirements

This is a .github/workflows/** filename-only change with no logic modified; neither .github/** nor
scripts/** is in Codecov's coverage.include (codecov.yml), so there is no codecov/patch
obligation. Verification: npm run actionlint passes on the renamed file (unchanged content, so this
should be a no-op), and git diff --check / a repo-wide grep for the old filename comes back empty.

Expected Outcome

The workflow's filename in .github/workflows/ matches its actual, documented manual-only nature (and
its own name: field), instead of implying a nightly schedule that was removed without a matching
rename.

Links & Resources

• .github/workflows/self-host-nightly.yml (the file to rename)
• Issue Generalize the self-host-nightly workflow beyond a single URL #4899 (closed) — "Generalize the self-host-nightly workflow beyond a single URL", the PR that
  generalized this workflow; this issue only fixes the stale filename left over from that or a later
  change, not a duplicate of it.

[linear-code]

JSO-5897