docs: add CLAUDE.md and mark display management as transitional

Signage had no agent guidance at all. Add a CLAUDE.md that records the
standalone-module architecture, that the parent ROADMAP.md and DESIGN.md are
authoritative, the ownership, branding, token, dark-mode, no-native-dialog and
plain-language rules, that display pairing is transitional until Stage 1
Settings -> Displays, and the branch-per-PR, no-push-to-main, no-release-tag
workflow.

The README listed a mobile management UI as out of scope, which contradicts
the design contract's responsive requirement; it is a Stage 1 deferral, and
now says so alongside how displays work today.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

CLAUDE.md

@@ -0,0 +1,82 @@
+# CLAUDE.md
+
+Guidance for Claude Code (and other coding agents) working in this repository. It points at
+authoritative sources rather than restating them, because restated details drift. Inspect the actual
+source, tests, `package.json`, and CI workflow before relying on anything here or on memory of a
+prior session.
+
+## What this repository is
+
+Signage is a first-party Ekklesia **module** in its own repository (`Zayin/Signage`). It is not part of
+the platform monorepo and vendors none of it: it builds against the published `@ekklesia/*`
+module-development packages (platform ADRs 0053 and 0054), ships as one Ekklesia Module Package
+(ADR 0049), and reaches PostgreSQL only through the Module Database ABI v1 executor the host hands it
+(ADR 0050). Read `README.md` for what exists and the scope boundaries.
+
+Signage owns its domain: channel groups, audience channels, timelines, slots, signage assignments,
+playback rules, native images, and **its own management and display UI**. The platform shell hosts
+that UI through the generic module loader and never rebuilds it; do not move Signage screens into the
+platform.
+
+## Product direction lives beside this repository
+
+The current roadmap and product/interface design contract are `ROADMAP.md` and `DESIGN.md` in the
+parent development directory (`../ROADMAP.md` and `../DESIGN.md` in the standard
+`~/development/ekklesia/` layout). They are deliberately **not** committed here; do not copy them in.
+They are authoritative for product direction. If this repository's documentation disagrees with them,
+flag the conflict and correct the repository-local documentation; never silently follow stale text.
+
+Rules from those documents that apply to every change here:
+
+- **Shared resources belong to the platform.** Displays/devices, identity, branding, mail, storage,
+  and module lifecycle are the platform's. Signage *consumes* displays; it assigns content to them.
+- **The current display management is transitional.** Signage's viewer roster, display naming, and
+  pairing instructions, together with the platform's sidebar *Display devices* panel, are what exists
+  today. Stage 1 moves pairing and the one global display name to the platform's
+  **Settings → Displays**, and Signage then selects an existing display. Fix defects in the current
+  flow, keep existing paired displays, viewer identities, cached content, and assignments working, and
+  do **not** implement the Stage 1 Settings/Displays architecture early.
+- **Branding.** Normal user-facing UI never hard-codes "Ekklesia" (platform ADR 0046).
+- **Visual direction.** Simple and minimal; responsive; light, dark, and system modes. Normal UI
+  colours come only from the shared design tokens (`@ekklesia/design-tokens`) and shared elements
+  (`@ekklesia/ui`) — never a hard-coded colour. The display artifact's pure-black stage, blackout,
+  and slate are content presentation, not themed UI.
+- **No browser-native dialogs.** `window.alert`, `window.confirm`, and `window.prompt` are prohibited.
+  Destructive actions use in-product confirmation proportional to impact: a two-step in-place
+  confirmation for moderate actions, the shared `Dialog` for significant ones.
+- **Plain language.** Normal church staff must understand the UI without implementation terms; do not
+  expose an internal identifier merely because it exists.
+
+## ADRs
+
+`docs/architecture/decisions/` holds Signage's own ADRs; the platform's ADRs live in the Ekklesia
+repository. Accepted ADRs are immutable except for status and cross-reference corrections. A changed
+decision gets a new ADR that supersedes the old one; never rewrite a historical ADR to fit a change.
+
+## Working conventions
+
+- Canonical remote: `ssh://[email protected]:2222/Zayin/Signage.git` (the platform is
+  `Zayin/Ekklesia.git`). Local clones can be behind: `git fetch --prune --tags` and branch from
+  `origin/main`.
+- One branch per PR off an up-to-date `origin/main`. Never push to `main`, never merge your own PR,
+  and never create or push a release tag — release tags belong to the human maintainer.
+- A fix that needs a platform contract change is two PRs: the Ekklesia change first, then Signage,
+  with the compatibility boundary explicit. Do not copy platform logic into Signage to avoid it.
+- Every defect fix gets a regression test. Signage never reads the environment, opens its own socket,
+  builds an Ekklesia URL, or applies a migration; all of that reaches it through the host.
+
+## Verification
+
+`package.json` and `.gitea/workflows/ci.yml` are the source of truth. From a clean checkout:
+
+```bash
+pnpm install --frozen-lockfile
+pnpm lint && pnpm typecheck && pnpm test && pnpm build && pnpm validate
+bash ci/check-cleanup.sh
+```
+
+The CI `integration` job installs the real Module Package into the pinned platform
+(`ci/platform.env`) and drives the Dashboard and a kiosk display in real browsers, running the display
+scenarios listed in `ci/display-scenarios` (`bash ci/package.sh`, `bash ci/fetch-platform.sh`,
+`bash ci/integration.sh`; it needs Docker). Unit tests passing is not evidence that a display or
+browser behaviour works: verify display behaviour through the integration harness.