…uring polling

Enable the mergeQueue feature flag and make the whole feature respect it:
useMergeQueueStatus, the sidebar's per-repo query and the GitHub panel's queue
tab were all polling Supabase regardless of the flag, and the panel's tab is
now hidden entirely when it is off.

Add a cloud-stored per-repo opt-in (007_merge_queue_enabled.sql) exposed as
get/set_merge_queue_enabled RPCs. A repo with no config row reads as OFF, so
the merge queue has to be switched on from the GitHub panel's Merge Queue tab
before 'Add to Queue' appears on a workspace or anything can be enqueued.

Merge Queue tab:
- toggle is a Switch rather than a button
- entries are listed as PRs and grouped into stacks, each stack rendered as a
  block that states it merges bottom-up into its target
- entries and whole stacks can be removed from the queue; removing a branch
  mid-stack takes everything above it so nothing is left stranded

Also fixes defects found in QA: QueueEntryStatus was missing the 'merging'
enum value and carried a 'passed' value the entry enum never emits, leaving
merging branches with an unstyled grey sidebar dot; enqueue only invalidated
the workspace's own status query, leaving sidebar dots and the queue tab stale
until their next 30s poll; and the header no longer surfaces a 'Testing…'
label.

Screenshot specs cover the queue states, the tab with multiple stacked PRs,
removal, and a flag-off regression guard.

…ntegrations

The per-repo merge queue toggle now lives in the settings page as a GitHub
setting alongside the repositories card, rather than in the GitHub panel's
Merge Queue tab. The tab keeps the disabled state but only reports it and
links to Settings; it no longer owns the control.

Also shortens the workspace header's queued label to 'Queued' instead of
'Queue #N'.

… continuous queue rail

Settings > Integrations now uses one header per integration with its settings
listed directly beneath, instead of bordered cards. The merge queue sits under
the GitHub header alongside the connected-repositories row.

The disabled state is a CTA rather than a prompt: an eligible repo (Pro plan,
GitHub App installed) gets a primary 'Enable merge queue' button, and the
switch only appears once the queue is on. An ineligible repo gets the reason
-- upgrade to Pro, or install the App on this repo -- so the control is never
offered where it could only fail.

The Merge Queue tab draws the queue as one continuous vertical rail with a
status-coloured node per entry, following the stack panel's idiom. The line
runs unbroken across stack groupings down to the target branch, showing that
the whole queue is a single merge sequence; stacks are marked by inline
headers and an accent on their entries rather than by separate cards.

Keys GitHubIntegrationSettings' repository-loading effect on user.id instead
of the auth objects, so a caller whose useAuth returns fresh objects per
render no longer loops.

Rebased onto main (Storybook setup, sparse checkout, font update, and the
new max-3-capture-document-expectations / no-inline-comments-in-tests /
no-multiline-inline-comments lint rules landed there since this branch was
cut). Rebase itself was conflict-free; this addresses what the newer lint
rules and CI now catch:

- Extract GitHubPanel's merge-queue rendering into
  github-panel/MergeQueueTab.tsx, bringing GitHubPanel.tsx under the 500-line
  cap.
- Rewrite useDequeueBranches' sequential dequeue loop without an
  await-in-loop, using a promise-chained reduce (ordering is still strictly
  top-down, which is why it can't be Promise.all).
- Fix max-params/max-nested-callbacks in merge-queue-stacks.test.ts by giving
  entry() an options object and extracting branchNames()/stackBranches()
  helpers instead of nesting .map() calls three deep.
- Use array destructuring instead of indexing in buildQueueStacks.
- Remove comments from the two merge-queue .test.ts files (banned there) and
  collapse a few multi-line comments elsewhere to one line.
- Split two captureDocument() calls whose expectations grew past 3 into
  separate captures with their own names.

Also rebuilt the NAPI addon, which was stale against main's sparse-checkout
Rust changes and was failing test/integration/workspace/sparse.test.ts.

No behavioral changes: full suite (281 tests) and the screenshot suite (25
captures across 14 spec files) pass, and I re-verified the merge-queue
screenshots pixel-by-pixel against their (now split) expectations.