feat: give display devices their own paired identity

ADR 0033 gave Ekklesia a display host and ADR 0034 gave it a login page.
Together, the only way to light a television in a foyer was to sign a
human being into it and leave that session running on a screen anyone can
walk up to: a person's credentials on a wall, a person's session as the
thing signage depends on, and the display going dark when they are
revoked or their session simply expires.

A screen is not a person. Ekklesia now recognizes three principal classes
— anonymous, authenticated human, and managed device — and a device is a
first-class principal with its own credential and its own explicit
permissions. It has no email, no password, and no row in the identity
tables, and it satisfies the `authenticated` baseline never, so every
route that settles for "somebody is signed in" stays closed to it.

Device permissions live in their own table because
ekklesia_core_grant.user_id is a non-null foreign key into the user table
and making it polymorphic would rewrite the platform's central
authorization record to serve one narrow case. That is a schema decision,
not a second decision point: the evaluator gained one branch, so a device
is allowed or denied by the same function, with the same deny-by-default,
as anyone else — with no owner path it could reach and no baseline that
stands in for a grant.

The six-digit code is not the credential. It is printed across a screen in
a public hallway, so it is treated as public: it identifies a request to
an administrator and is worth nothing alone. Collecting the credential
also requires a 256-bit claim secret held only in the requesting browser's
HttpOnly cookie, and approving requires the restricted core.devices.manage
permission. Without that split, reading a code off a wall would hand over
the screen's identity.

The permission a pairing asks for is read from the module's validated
display declaration, never from the request, so a browser cannot ask to be
granted core.devices.manage or another module's permission. Approval
grants exactly that one permission.

Credentials are stored only as SHA-256; the raw value exists in the
Set-Cookie that issues it and the device's own cookie jar, and is never
logged, returned in JSON, or placed in a URL. The cookie is HttpOnly, so
the module display code running in that same page cannot read it.
Revocation is a server-side column checked on every principal resolution,
and re-pairing mints a new identity so an old credential can never come
back. State transitions are conditional updates, so one code cannot be
approved twice or claimed into two credentials under a race.

/api/v1/principal still reports a device as anonymous: it is what the
Dashboard uses to decide whether a person is signed in. Displays read
their viewer from the descriptor instead, which already performed the
authorization — so displays are descriptor-first while the Dashboard stays
principal-first, and neither infers an identity by elimination.

Proven end to end against real PostgreSQL and real HTTP: an unpaired
screen shows a code, an owner approves it, the device opens the display
descriptor and a realtime stream, and revocation closes both while the
device still holds its cookie. An already-open SSE stream is bounded by
realtime's existing five-minute reconnect rather than closed instantly,
and that bound is documented rather than called immediate.

Co-Authored-By: Claude Opus 5 <[email protected]>

docs/development/testing.md

@@ -351,6 +351,30 @@ password arriving on standard input and never in `argv`, `--password` refused, a
 `DATABASE_URL`, and an unmigrated database refused rather than silently migrated — with assertions
 that neither stdout nor stderr contains the password or the connection string.
 
+A further suite (`apps/api/tests/device-pairing.integration.ts`, same harness) proves display device
+pairing end to end against real PostgreSQL and the real HTTP transport
+([ADR 0036](../architecture/decisions/0036-managed-device-identity-and-pairing.md)). None of it is
+mocked: a screen with no identity is refused the descriptor but served the page it needs, asks to be
+paired, and receives a code; a real platform owner — created by the Pass 1B bootstrap and signed in
+through the real login transport — looks the code up and approves it by name; the screen collects its
+credential from a real `Set-Cookie` and then opens the real display descriptor and a real realtime
+stream; and the owner revokes it, after which both fail while the device still holds its cookie.
+
+The suite also pins the properties that make the design safe rather than merely working: that the
+raw credential appears nowhere in the database or in any response body, that the permission is taken
+from the display declaration and not from a request that tried to name `core.devices.manage`, that
+someone who knows only the code (an onlooker reading a television) is issued nothing, that anonymous
+callers, a paired device, and a cross-origin administrator are all refused approval, that one code
+cannot be approved twice or claimed into two credentials under a race, that re-pairing produces a
+fresh identity while the old credential stays dead, and that a browser holding both a human session
+and a device cookie remains a person.
+
+Device authority itself is proven without a database in `core/tests/authorization-device.test.ts`,
+which is mostly a list of things a device must *not* acquire: authority from being a principal, from
+an `authenticated` baseline, from platform ownership, or from a user grant. Its ports are wired to
+answer "yes" to every human question, so any accidental fall-through into a human path would flip
+those assertions.
+
 ### Which kind of timing proof lives where
 
 Pass 4 introduced several deadlines, and their tests deliberately differ in kind: