fix: hide write UI resources in read-only mode

[he-yufeng]

Summary

• hide the issue/pr write UI resources when the server runs in read-only mode
• keep the read-only-safe get_me UI resource registered
• add a regression test for the resource list returned by RegisterUIResources in read-only mode

Fixes #2519.

To verify

• go test ./pkg/github -run "Test(RegisterUIResources|NewMCPServer_RegistersUIResources)" -count=1
• git diff --check origin/main...HEAD

[advancedresearcharray]

Rebased this branch onto current main and validated locally.

Rebased commit: b5e2b7b (based on latest github/github-mcp-server main)

Validation (Go 1.25):

• go test ./pkg/github -run "Test(RegisterUIResources|NewMCPServer_RegistersUIResources)" -count=1 — pass (TestRegisterUIResources_ReadOnlySkipsWriteResources; UI-asset tests skip without script/build-ui)
• go test ./... -count=1 — pass
• git diff --check upstream/main...HEAD — clean

To update this PR branch:

git fetch https://github.com/advancedresearcharray/github-mcp-server.git fix/read-only-ui-resources-v2
git checkout fix/read-only-ui-resources-v2
git reset --hard FETCH_HEAD
git push --force-with-lease origin fix/read-only-ui-resources-v2

This should trigger CI on the PR. The branch is currently mergeable with main; only maintainer review is blocking.

Note: #2581 is an older duplicate of the same fix and is behind main — consider closing it in favor of this PR.

[SamMorrowDrums]

Thank you for this! Much appreciated. 🙏