Upgrade swarm: role-aware dispatch, specialist roles & structured system prompts

[justrach]

Summary

• Fix: workers now use orchestrator-assigned roles — previously all workers ran as fixer regardless of what the orchestrator decomposed. Now workerFn passes args.worker.role to resolveWithProbe(), so each agent gets the right system prompt, model tier, and read/write permissions.
• Orchestrator is role-aware — prompt now lists all 12 available roles with descriptions and read/write capabilities. Also dispatches as "orchestrator" role (picks up bolt/gpt-5.4 from grid).
• 4 new specialist roles added to roles.zig and grid.zig:
  • safety_auditor (opus) — memory safety: UAF, double-free, allocator mismatch, silent OOM
  • zig_specialist (sonnet, writable) — errdefer, slice ownership, allocator lifecycle
  • api_reviewer (sonnet) — ownership semantics, return lifetimes, doc accuracy
  • test_writer (sonnet, writable) — regression tests with leak detection
• All 12 role prompts rewritten with structured format:
  • WHEN TO USE / GUIDELINES / RULES sections
  • Checklists for reviewers and auditors
  • "Simple-first, reuse-first, read-before-write" for fixers
  • Scope limits and post-edit verification gates
  • Severity-ranked output (HIGH/MEDIUM/LOW)

Test plan

• zig build test passes locally
• CI zig build test check

🤖 Generated with Claude Code