fix: scope Codex enrich prompts to active triage clusters

[ApexWorm]

Problem

The generic Codex enrich runner received the full plan and its prompt encouraged a global cluster listing. During a frozen/recovered triage session, that could lead the runner to enrich historical clusters unrelated to the active review issues.

Fix

• Render an explicit Active Enrich Scope from the frozen session using scoped_manual_clusters_with_issues(plan, state).
• Instruct enrich workers to mutate only the named active clusters and treat the global cluster list as historical context.
• Keep a fully stale frozen session from falling back to every manual cluster.

Validation

• python3 -m pytest desloppify/tests/commands/plan/test_triage_runner.py -q (54 passed)
• ruff check desloppify/app/commands/plan/triage/runner/stage_prompts.py desloppify/app/commands/plan/triage/runner/stage_prompts_instruction_blocks.py desloppify/tests/commands/plan/test_triage_runner.py