feat(client): read the public catalogue with a publishable key

[fuzcap]

The client side of kaitencloud/kaiten#32: in public mode (authScheme: "publishable", a pk_ key), components.getCatalog() now reads GET /api/public/catalog, the only route a publishable key authorizes. Before this, public mode asked GraphQL, which answers 401 to a pk_.

Stacked on #2 (feat/billing).

Behaviour

• Public mode sends X-Kaiten-Publishable-Key to /public/catalog and nowhere else. It never falls back to GraphQL or the REST fan-out: both refuse the key, and the key has no business being sent there (billing spec §14.6.1). A refused key rejects with the API's 401/403, and onDegraded does not fire.
• Bearer mode reads the catalogue exactly as before.

Mapping (§14.5)

API	SDK
default MONTHLY / ANNUAL FLAT_FEE unitAmount	Plan.price / Plan.annualPrice, minor units
billingPeriod	interval, plus new intervalCount (quarterly = month × 3, semi-annual = month × 6)
currency	currencyCode
familySlug	Plan.familyId
lifecycleState	published, lifecycleState
entitlement type + inner value	EntitlementValue ({ type: "number", value }), unlimited, presentation fields
compatibleAddonFamilies	Plan.addOns, resolved against the public add-ons

All new fields are optional, so the client stays on 1.x:

• PlanPrice: id, intervalCount, unitAmountDecimal, billingModel, meteredEntitlementSlug, saleUnitFactor, isDefault;
• Plan: pricingType, selfServe, selfServeCtaUrl, trialPeriodDays, requiresPaymentMethod;
• Addon: familySlug, maxQuantity;
• KaitenCatalog: addOns, capabilities.

⚠️ One deviation, for the components

§14.5 says a fractional-minor-unit price (unitAmount absent, e.g. €0.005 per token) must never go into amount. But PlanPrice.amount is a required number, and making it optional would break every consumer's types. So such a price carries the exact decimal in unitAmountDecimal, and amount is that same fraction as a number (0.5), documented on the field. Components must format metered prices from unitAmountDecimal, per sale unit, and never add them to a headline. Flat fees are always whole minor units, so price/annualPrice are unaffected.

For the React SDK (PricingTable)

• Read plan.selfServe: when false, render plan.selfServeCtaUrl ("Contact us"), always for pricingType: "CUSTOM".
• Metered prices are the ones with billingModel USAGE_BASED/OVERAGE. Render them "per saleUnitFactor units", not as a monthly headline.
• catalog.capabilities.checkout is false until customer sessions ship.

Notes

• The wire types live in src/client/public-catalog.ts, written by hand. contracts/openapi.yaml follows released kaiten versions and this route is newer; when contract-drift brings it in, the generated types can replace them and the mapping stays.
• Six existing catalogue tests used publishable mode as convenient setup for the GraphQL/REST path. They now construct a bearer client, which is the path they test.

Tests

• vp run -r build && vp check && vp test: 221 passing.
• New tests:
  • the request goes to /public/catalog with the key and no Authorization;
  • the mapping: headline prices, quarterly interval, fractional overage, unlimited entitlement, add-on resolution;
  • no fallback after a 401.