fix: skip CI MCP server installation when actions:read permission is missing

[OctavianGuzu]

Problem

The github_ci MCP server calls GET /repos/.../actions/runs at startup. When the workflow lacks actions: read permission, GitHub returns a 403, which crashes the MCP server and causes the entire Claude Code process to exit with code 1 ("SDK execution error").

The permission check (checkActionsReadPermission) already existed and logged a warning, but the server was registered unconditionally — so the warning fired and then the server crashed anyway.

Fix

Move the CI server registration into the else branch of the permission check, so it's only installed when actions: read is confirmed. When the permission is missing, we log a warning with actionable guidance and skip installation entirely.

[claude]

nit: Since this PR changed the warning text, it would be worth asserting that core.warning was called with the expected message (e.g., matching "Skipping CI server installation"). This would guard against regressions in the warning behavior and confirm the graceful-degradation UX, not just the config output.

[claude]

nit: The guidance here covers adding actions: read to the workflow's permissions: block, but users of this action also need to set additional_permissions: 'actions: read' in the action's with: inputs (per docs/usage.md). Consider linking to the project's own configuration docs instead of (or in addition to) the generic GitHub token docs, so users can find both steps in one place.

[claude]

Review Summary

Clean, well-scoped fix. The core change — moving CI server registration into the else branch of the permission check — is correct and addresses the crash described in the PR. The warning message is improved (actionable guidance instead of a vague request), and the new test covers the key scenario.

No blocking issues. Two nits left as inline comments:

1. Test: The new test verifies github_ci is excluded on 403, but does not assert that core.warning was called. Since this PR changes the warning text, asserting on it would guard the full behavior.
2. Warning message: The guidance mentions adding actions: read to workflow permissions but omits the additional_permissions action input that is also required. Linking to the project docs would help users find both steps.

One broader observation (pre-existing, not introduced by this PR): the global.fetch mock in beforeEach intercepts all fetch calls across the entire test suite. Today this works because non-CI tests do not reach checkActionsReadPermission, but it could silently mask issues if future tests trigger fetch-based calls. Something to keep in mind for future test additions.