feat(core): gitea read client behind an injected fetch (#1)

createGiteaClient(config, fetchImpl).getIssue(index) fetches one issue
and normalizes raw gitea JSON to a typed GiteaIssue with scheduler
facts precomputed via extractLabelFacts. Network is an injected
FetchLike (core has no DOM lib; global fetch is structurally
assignable), so it unit-tests against a stub — no live calls in the
suite. Non-2xx responses throw GiteaApiError carrying status + body.

Closes P1-1. Verified end-to-end against the live repo's issue #9.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/core/src/index.ts

@@ -8,3 +8,15 @@ export {
   parsePriorityLabel,
 } from './labels/label-schema.js'
 export type { EstimateLabel, LabelFacts, PriorityLabel } from './labels/label-schema.js'
+
+export { createGiteaClient, normalizeIssue } from './gitea/client.js'
+export type { GiteaClient } from './gitea/client.js'
+export { GiteaApiError } from './gitea/types.js'
+export type {
+  FetchLike,
+  GiteaConfig,
+  GiteaHttpResponse,
+  GiteaIssue,
+  GiteaMilestoneRef,
+  GiteaRequestInit,
+} from './gitea/types.js'