feat(sidebar): drag-and-drop connection reordering (#748)

[Asgabani]

Closes #748.

What changed

• StorageData.connection_order (new collection): a flat list of connection ids in the user's preferred order, mirroring the existing dismissed_seeds-style separate-list pattern rather than a field on DatabaseConnection — a managed:true connection is replaced wholesale on every load (see mergeManagedConnections), so a field on the connection object itself would be silently discarded on reload.
• storage.getConnectionOrder() / storage.setConnectionOrder() on the storage facade, wired into useStorageSync's migrate/pull paths like every other collection.
• applyConnectionOrder() (src/lib/connection-order.ts): sorts a connections array by the persisted order; a connection absent from the order (never dragged, or created after the user last reordered) sorts after every connection the order does know about, in its original relative position (Array.prototype.sort is spec-stable, so that fallback needs no code of its own).
• useConnectionOrder() hook: useSyncExternalStore over the facade, same shape as the repo's other storage-backed hooks.
• ConnectionsList / ConnectionItem: native HTML5 drag-and-drop (no new dependency) — a drag handle appears on hover once onReorderConnections is passed and the list has more than one connection; dropping persists the new order via the facade.

Note on #694

#748's "Done when" mentions #694 (favorites): if that lands first, a favorited group should keep its own drag order rather than the two features competing for one order field. Since #694 hasn't merged yet, this PR reorders the flat connections list only. connectionOrder/onReorderConnections are threaded through as plain optional props (not baked into any favorites-aware grouping), so whichever PR lands second can partition the already-ordered list into favorite/non-favorite groups without this one needing to change.

Testing

Ran locally (bun run format && bun run lint && bun run typecheck && bun run knip && bun run chart:check && bun run channels:showcase:check && bun run readme:check && bun run security:check && bun run test && bun run build, plus bun run build:lib && bun run attw):

• format / lint / typecheck / knip: clean. Lint warning count unchanged from a clean checkout (189, compared via git stash).
• All four drift guards (chart, channels showcase, readme, security): pass.
• bun run test:components: 39/39 groups pass.
• bun run test: same 13 pre-existing failures as a clean checkout (Helm binary not installed, missing built standalone zip) — verified identical via git stash before/after. No live Postgres/MySQL in this sandbox, so DB-integration tests weren't exercised beyond what's already mocked.
• bun run test:coverage && bun run coverage:check: 100.00% line coverage on the merged lcov.
• bun run build, bun run build:lib, bun run attw: all succeed (ConnectionsList/Sidebar are reachable from the embeddable workspace export surface).

If CI surfaces something this sandbox couldn't (Helm chart tests, live DB integration tests), happy to fix it up.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[cevheri]

Good work, @Asgabani. I ran it in the app in Chromium and in Firefox: the handle on hover, dragging up and down, the order surviving a reload, a connection created afterwards appending last, and a drag never selecting the row. onDragStart does not call dataTransfer.setData, which used to stop Firefox starting a drag at all, and Firefox 155 is fine without it. Two things before I merge.

1. storage.deleteConnection does not prune connection_order. I deleted a connection through the UI and its id was still in the stored order afterwards, and it keeps being pushed to server storage. deleteConnection is already where a sibling id list is maintained on delete: dismissed_seeds is recorded there. Same place, with a test.

2. docs/STORAGE.md is the collection inventory and it still describes ten: the collection column enumeration, the "10 collections" line and the table under it, the localStorage key map, the facade API row for Connections (it already lists getDismissedSeeds()), and the second "10 collections" in the migration walkthrough. Two code comments count them too: encrypting-provider.ts says "the remaining six hold metadata", which is the written justification for encrypting only connections, and connection-secrets.ts says "all ten collections". #812 adds a collection as well, so whichever of the two lands second has to re-derive that number rather than write 11.

One note, no change needed: the mobile list gets the props, but HTML5 drag is pointer-only, so nothing there can fire on a phone. The handle needs hover, so nothing looks broken either.

[Asgabani]

Addressed both:

1. `deleteConnection` now prunes the deleted id out of `connection_order` too, mirroring the existing `dismissed_seeds` handling, with tests.
2. `docs/STORAGE.md`'s collection inventory is updated everywhere it counted collections (schema table, collection reference table, localStorage key map, facade API row, both "10 collections" call-outs), plus the two code comments in `encrypting-provider.ts` and `connection-secrets.ts`. This PR's own count is 11 (favorites doesn't exist on this branch yet) — whichever of feat(sidebar): add a favorite/pin toggle for connections #812/feat(sidebar): drag-and-drop connection reordering (#748) #817 you merge second will need a quick recount to 12, as you flagged.

Rebased onto latest `main` — that pulled in a new `tests/components/studio/source-tab.test.tsx` whose storage mock predates this branch and was missing the two methods `useConnectionOrder` calls, so I added those too (unrelated to your feedback, just needed to keep tests green post-merge).

Ran the full local suite again: format/lint/typecheck/knip clean, all four drift guards pass, `test:components` 46/46 groups, core suite at the same pre-existing 13 environment-gap failures (Helm/standalone-zip) as a clean checkout, 100.00% coverage, build green.

[cevheri]

merging shortly, fixed conflicts

[cevheri]

Thanks @Asgabani. #812 landed first, so I merged main into this branch and pushed two commits on top of yours rather than asking you for another round.

The merge keeps both sides. The collection inventory is now 12 in docs/STORAGE.md, and the two code comments say "eight" and "twelve".

The follow-up commit is where the two features meet. Favorites and Connections are both cut from the one saved order, so each section keeps your order within itself. A drop onto a row in the other section is ignored and that row is not highlighted, because the dragged row would stay in its own section and the only effect would be an invisible change to the saved order. A row alone in its section gets no handle. Tests are in ConnectionsList.test.tsx.