framework tools/git: enroll issue-comment suites in framework-shell CI

Codex review of a27b7dc9 (blocker): check-test-enumeration.sh rejects
unenumerated test files.

- test-issue-comment-usage-contract.sh enrolled in test:framework-shell
  (hermetic by construction: PATH stubs, sandboxed runner, no network).
- test-issue-comment-readback.sh enrolled and its stale exclusion removed.
  The exclusion's own note anticipated this: 'joins CI after the
  wrapper-half hermeticity fix' - that fix (neutralizing seat-exported
  MOSAIC_GIT_IDENTITY / MOSAIC_BRAIN_HOME that escape the sandboxed HOME)
  landed in a27b7dc9. Suite green in brain and worktree trees tonight.

Enumeration guard: OK (population 73, enumerated 60, excluded 14).

packages/mosaic/framework/tools/quality/test-enumeration-exclusions.txt

@@ -14,7 +14,6 @@
 packages/mosaic/framework/tools/git/test-pr-merge-gitea-empty-uid.sh | resolves real credentials (#1007 census); joins CI after the wrapper-half hermeticity fix (git -C scoping)
 packages/mosaic/framework/tools/git/test-issue-create-interactive-auth.sh | resolves real credentials (#1007 census); joins CI after the wrapper-half hermeticity fix
 packages/mosaic/framework/tools/git/test-pr-metadata-gitea.sh | resolves real credentials (#1007 census, fourth entry via family-grep); joins CI after the wrapper-half hermeticity fix
-packages/mosaic/framework/tools/git/test-issue-comment-readback.sh | resolves real credentials (#1007 census, fifth entry); joins CI after the wrapper-half hermeticity fix
 
 # --- tools/git: push guards — measured green locally, CI-image fitness unverified ---
 packages/mosaic/framework/tools/git/test-push-guard.sh | measured green at 826a8b3b (46 passed / 0 failed, one run, 2026-07-31); CI-image fitness unverified; #1017 burndown