fix: normalize Forgejo PR/issue state to uppercase

Forgejo REST API returns state as lowercase ("closed"/"open") but
branch.ts compares against GraphQL-style uppercase ("CLOSED"/"MERGED").
This caused @claude on closed/merged PRs to take the open-PR checkout
path, failing with "fatal: invalid reference: refs/pull/N/head".

Normalize state to uppercase in the Forgejo data fetcher, matching the
existing pattern used for review state (line 153).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/forgejo/data/fetcher.ts

@@ -300,7 +300,7 @@ export async function fetchForgejoData({
       lastEditedAt: undefined,
       additions: pr.additions,
       deletions: pr.deletions,
-      state: pr.state,
+      state: pr.state.toUpperCase(), // Normalize to uppercase (Forgejo REST returns "closed"/"open", branch.ts expects "CLOSED"/"MERGED")
       labels: {
         nodes: (pr.labels ?? []).map((l) => ({
           name: typeof l === "string" ? l : (l.name ?? ""),
@@ -352,7 +352,7 @@ export async function fetchForgejoData({
       createdAt: issue.created_at,
       updatedAt: issue.updated_at,
       lastEditedAt: undefined,
-      state: issue.state ?? "open",
+      state: (issue.state ?? "open").toUpperCase(), // Normalize to uppercase for consistency with GraphQL conventions
       labels: {
         nodes: (issue.labels ?? []).map((l) => ({
           name: typeof l === "string" ? l : (l.name ?? ""),