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]>

packages/module-ui-sdk/src/host-context.ts

@@ -54,10 +54,15 @@ export type ModuleUiPrincipal =
  * Everything a host hands a module's UI, and the complete list of what module UI may assume exists.
  *
  * This is deliberately the smallest set that proves the architecture rather than everything a real
- * screen will eventually want. Navigation, host theme and design tokens, module configuration,
- * organization/platform context, and diagnostics reporting are **not** here yet: each needs a design
- * that does not exist, and a speculative field frozen into a public contract is harder to remove
- * than to add. See ADR 0022.
+ * screen will eventually want. Navigation, module configuration, organization/platform context, and
+ * diagnostics reporting are **not** here: each needs a design that does not exist, and a speculative
+ * field frozen into a public contract is harder to remove than to add. See ADR 0022.
+ *
+ * The host **theme** is deliberately absent for a different reason. Design tokens reach a module as
+ * inherited CSS custom properties, not as data (ADR 0039): the host installs the values at its own
+ * root, they inherit into the artifact's own root, and module code writes `var(--ekklesia-…)`. A
+ * token map on this context would make styling a run-time negotiation, force every module to
+ * re-implement it from data, and give a host something it could forget to supply.
  *
  * Nothing in this object is an Ekklesia implementation. Every member is satisfiable by a standalone
  * host that never runs Core, which is what makes one module UI hostable by both. The same context is