[pikann]

Summary

Adds issue listing to the GitLab provider, so Paca's issue_list tool (and any other caller of the optional issue-list capability) works for GitLab projects the same way it does for GitHub. Before this, the provider could read one issue by number but could not list them.

Changes

• ListIssues (spi_reads.go). Implements gp.IssueLister against GET /projects/:id/issues:
  • state maps open → opened; closed and all pass through; an empty state means open; anything else is a validation error;
  • scope=all, newest first (order_by=created_at&sort=desc);
  • paginated with the existing paged and nextPage helpers, so the cursor follows the raw page size (GitLab's issues endpoint returns issues only, so a page needs no filtering).
• Shared issue mapping. A glIssue type with toIssue() replaces the anonymous struct and state mapping that GetIssue carried, so GetIssue and ListIssues return identical shapes.
• Capability. Describe() now declares IssueList: true and spi_assert.go asserts gp.IssueLister. The SDK conformance suite requires the interface and the capability to be declared together; both are, alongside the existing IdentityDescription.

Compatibility

• Needs no SDK bump (already on plugin-sdk-go v0.4.2), and no manifest, data or migration change.
• A host that does not know the capability ignores it. One that does can now list GitLab issues.

Tests

• spi_fakegitlab_test.go: the fake GitLab serves an issue list.
• spi_issues_test.go (new): paging and the open/closed/all state mapping; an invalid state or cursor is a validation error and an upstream 403 is propagated; IssueList is declared.
• go vet, go test ./... and GOOS=wasip1 GOARCH=wasm go vet . pass.