Add the stale devices page

[yolanfery]

Closes #2.

What changes for the user

A new Stale devices page, at /stale-devices, lists every device whose last sync is older
than N days — oldest first, with its serial, facility, district, last sync and last user. A
supervisor can now see the absence of a sync, which /syncs never showed: a device that stopped
three weeks ago simply drifted off the top of that list.

Devices that never synced have no sync row at all, so every join written so far dropped them.
They get their own block below, folded by default and showing its count: a standing inventory
problem rather than today's call list.

The number of days lives in the URL (?days=14), so a supervisor can bookmark a view or send it
to a colleague. A hand-edited or missing value falls back to 7 instead of erroring.

How it works

• The query — src/features/stale-devices/api/queries.ts. Each device's newest sync comes from
  a LEFT JOIN LATERAL ... LIMIT 1: a subquery allowed to refer to the row it is joined to, the
  shape a Django developer writes with Subquery and OuterRef. It walks the existing
  device_sync (device_id, synced_at desc) index, yields exactly one row per device, and LEFT
  keeps the never-synced devices with nulls. now is a parameter, never now() in the SQL, so a
  test can choose the date.
• The components — StaleDeviceTable takes props and is rendered twice, once per block; a null
  lastSyncedAt renders as "never". NeverSyncedSection owns the open/closed state, which keeps
  the page free of state and puts the fold where the repository says to test it.
• The page — the number box reads the URL and writes it back with replace, so there is no
  useState, no useEffect, and the back button is not filled with every digit typed.
• Registration — one line in src/features/router.ts and one in src/features/nav.ts.

Tests

Queries on an in-process Postgres, components in jsdom. The route, the page and the tRPC procedure
get none, per CLAUDE.md. The boundary cases are the interesting ones: a device exactly at the
cutoff (excluded — "older than", not "older or equal"), a device judged on its newest sync rather
than an older one, and a never-synced device returned whatever N is.

pnpm test — 56 tests, 15 files, green. pnpm exec tsc --noEmit — clean.

ADRs

• 0015-page-state-lives-in-the-url.md
• 0016-lateral-join-for-the-latest-row.md

Out of scope

Filtering by district or user (#17, #19), the map (#3), a device detail page (#6). No pagination:
the fleet is 200 devices, so the whole list fits.

Spec: docs/superpowers/specs/2026-09-18-stale-devices-design.md
Plan: docs/superpowers/plans/2026-09-18-stale-devices.md

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Project	Deployment	Actions	Updated
wee-app	Ready	Preview	Sep 18, 2026 9:29am UTC

[yolanfery]

Review round done. No Critical findings; the three Important ones are fixed in 53c78c6, 7612328 and 07ca4e4.

• Changing the threshold blanked the page. useQuery is keyed on the threshold, so each keystroke swapped in an empty cache entry: the result block unmounted behind a spinner and the never-synced section, which owns its open/closed state, refolded itself. placeholderData keeps the previous rows until the next ones arrive.
• The lateral had no tie-break. Two syncs sharing a timestamp left the planner to choose which one named the last user, so the name to call could change between two loads. Added .orderBy('sync.id', 'desc'), as listRecentSyncs already does.
• Two test gaps. Nothing pinned lastUsername to the newest sync, and nothing pinned the serial ordering of the never-synced block — the whole block ties on a null last sync, so the serial is the only thing ordering it. Three query tests added; I checked the new ordering test fails when the orderBy is removed.

Minors taken: the plural of "1 day", allowDecimal={false} on the number box (a typed "." made it snap back to 7), the fold triangle hidden from screen readers with aria-hidden plus aria-controls, and the third fold test now asserts the rows actually leave the document rather than re-checking aria-expanded. ADR 0015 said the back button works, which replace: true deliberately prevents; reworded. The plan file records what changed after it was written.

Minors left: the district inner join would drop a device (or error on ''::int) if an org_unit_id ever pointed somewhere other than a level-4 facility — pre-existing, shared with listRecentSyncs, and the seed guarantees the invariant; and clearing the number box to retype snaps the old value back.

59 tests green, tsc clean.