feat: give every Ekklesia screen one set of design tokens and elements

Modules have owned their own UI since ADR 0021, but the platform has never
said what that UI should look like. Every screen here — the Dashboard shell,
the display host, the module template — invented its own hex colours, font
stack, spacing, and radii, and they already disagreed. A module author had no
vocabulary for "the ordinary panel background", so the only available answer
was to invent one, and two modules would invent two.

Add `@ekklesia/design-tokens`: one validated, enumerable registry of semantic
tokens. A token declares a name, label, description, and default value; its
category and `--ekklesia-*` identifier are derived from the name, so it can
never claim one category while being named for another. Construction rejects
duplicates, malformed names, unknown categories, empty or overlong text, and
any value that is not a bounded literal — no declaration terminator, rule
block, comment, at-rule, `url(`, `!important`, escape, control character, or
markup. A registry that constructs can therefore be emitted as CSS without
escaping, because nothing needing escaping can be in it. That validation is
also what makes a future theme editor implementable rather than aspirational.

Add `@ekklesia/ui`: button, icon button, text input, select, checkbox, field
wrapper, panel, dialog, tabs, table and list primitives, badge, toast, and
empty/error/loading states — every value a token reference, with real
`:focus-visible` treatment and status that never depends on colour alone.
Deliberately small: an element earns its place when two consumers need it.

The stylesheet is a string rather than a `.css` file so the identical bytes
install into a document or an isolated artifact root, and so hover, disabled,
and focus-visible are real CSS rather than JavaScript approximations of them.

`pnpm boundaries` opens exactly two shared roles to modules, by name — every
other role stays rejected — and pins both design packages to the bottom of the
presentation stack. Both are browser-safe by construction, proven by a real
compile of module-shaped source in which `process.env` must fail to typecheck.

The shell installs the defaults at its document root for the Dashboard and the
display; custom properties inherit into module artifacts, so a module reads
`var(--ekklesia-…)` with nothing to import at run time and nothing for a host
to forget to pass.

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

CONTRIBUTING.md

@@ -42,6 +42,11 @@ pnpm infrastructure:config
   the v6 manifest declares via `@ekklesia/module-ui-build` (ADR 0023/0033). Module authors write no
   bundler configuration, and styling is React inline style objects only for now. Both roles use the
   same UI SDK context with no presentation-mode flag.
+- A module may also consume exactly two shared design packages — `@ekklesia/design-tokens` and
+  `@ekklesia/ui` (ADR 0039) — so two modules' screens look like one product. That is a named
+  allowlist: every other shared role (`api-client`, `auth-client`, `surface-sdk`, `module-ui-host`)
+  stays rejected inside a module. Reference registered semantic tokens; never define an
+  `--ekklesia-*` custom property of your own.
 - Module UI reaches its host only through `@ekklesia/module-ui-sdk` — never
   `@ekklesia/module-ui-host`, which is the host-side loader — and asks the host for its own
   API by relative path — never by constructing `/api/v1/modules/<id>/...`, which is Ekklesia's