Fill frontend rule gaps and broaden v2 tokens

Add the frontend guides the v2 UI kit and compliance-portal need but
that the first rework left uncovered: forms, routing, client state, and
permission-gated UI.

forms.md documents a tiered approach on Base UI Field/Form -- native
constraints, then a validate function, then zod parsed in onSubmit, and
react-hook-form only for large or dynamic forms -- and drops the custom
useFormWithSchema wrapper. routing.md covers @probo/routes, navigation,
typed params, URL-as-state, redirects, auth/protected routes, and the
folded-in no-outlet-context rule. state-management.md gives a decision
order across Relay, URL, local state, context, and zustand.
permissions.md gates UI on the canUpdate/canDelete permission(action:)
fields without re-encoding authorization in the client.

Rename v2-colors.md to v2-tokens.md and add the typography, radius,
shadow, and native-spacing scales alongside color. Extend ui.md with
user feedback, empty-state, and accessibility sections; standardize
toasts on Base UI's Toast (Toast.useToastManager) and retire the legacy
useToast across ui.md, forms.md, error-handling.md, and relay.md. Add an
Intl formatting section to i18n.md and a non-Relay HTTP / file
upload-download section to ts-style.md. Update the AGENTS.md index and
the v2-color-scale cursor rule for the new and renamed guides.

Signed-off-by: Émile Ré <emile@probo.com>

AGENTS.md

@@ -5,7 +5,7 @@ Detailed guides for specific subsystems live in `contrib/claude/`:
 - [`contrib/claude/make.md`](contrib/claude/make.md) — GNUmakefile targets, codegen, overridable variables
 - [`contrib/claude/api-surface.md`](contrib/claude/api-surface.md) — GraphQL / MCP / CLI / n8n sync rules
 - [`contrib/claude/go-style.md`](contrib/claude/go-style.md) — Go project deps, style (declarations, calls, imports, errors, naming, logging, safe URL construction)
-- [`contrib/claude/ts-style.md`](contrib/claude/ts-style.md) — TypeScript style (safe URL construction)
+- [`contrib/claude/ts-style.md`](contrib/claude/ts-style.md) — TypeScript style (safe URL construction, non-Relay HTTP, file upload/download)
 - [`contrib/claude/go-testing.md`](contrib/claude/go-testing.md) — Go test conventions (parallel, require vs assert, naming)
 - [`contrib/claude/go-service.md`](contrib/claude/go-service.md) — Go service orchestration (Run, graceful shutdown, crash propagation)
 - [`contrib/claude/go-worker.md`](contrib/claude/go-worker.md) — Go worker pattern (poll-based, bounded concurrency, FOR UPDATE SKIP LOCKED)
@@ -24,9 +24,13 @@ Detailed guides for specific subsystems live in `contrib/claude/`:
 - [`contrib/claude/relay.md`](contrib/claude/relay.md) — Frontend Relay client (queries, fragments, mutations, pagination)
 - [`contrib/claude/react-components.md`](contrib/claude/react-components.md) — React component shape (file/export, props, configure vs data via hooks, naming/suffix taxonomy, error props)
 - [`contrib/claude/ui.md`](contrib/claude/ui.md) — @probo/ui v2 kit (Base UI headless, Tailwind, tailwind-variants, flat folders, bundle-safe skeletons)
-- [`contrib/claude/v2-colors.md`](contrib/claude/v2-colors.md) — v2 color system (Radix scale, step usage, do/don't)
+- [`contrib/claude/v2-tokens.md`](contrib/claude/v2-tokens.md) — v2 design tokens (color, typography, radius, shadow scales; native spacing)
+- [`contrib/claude/forms.md`](contrib/claude/forms.md) — Frontend forms (Base UI Field/Form tiers, native vs zod vs react-hook-form, server errors)
+- [`contrib/claude/routing.md`](contrib/claude/routing.md) — Frontend routing (@probo/routes, navigation, typed params, URL state, auth/protected routes)
+- [`contrib/claude/state-management.md`](contrib/claude/state-management.md) — Client state decision order (Relay, URL, local, context, zustand)
+- [`contrib/claude/permissions.md`](contrib/claude/permissions.md) — Permission-gated UI (canUpdate/canDelete permission(action:) fields)
 - [`contrib/claude/error-handling.md`](contrib/claude/error-handling.md) — Frontend error handling (ErrorBoundary at any level, error/fallback props, async try/catch)
-- [`contrib/claude/i18n.md`](contrib/claude/i18n.md) — Frontend i18next (key-based translations, _locales/<locale>.json per routes.ts)
+- [`contrib/claude/i18n.md`](contrib/claude/i18n.md) — Frontend i18next (key-based translations, _locales/<locale>.json per routes.ts, Intl formatting)
 - [`contrib/claude/config.md`](contrib/claude/config.md) — Configuration propagation (all files to update when config changes)
 - [`contrib/claude/file-naming.md`](contrib/claude/file-naming.md) — File naming conventions (template files, extensions)
 - [`contrib/claude/prompt-style.md`](contrib/claude/prompt-style.md) — Agent prompt template structure (role/task/instructions XML style)