1.6.0 — fix --dry-run and honest migrate feedback

Note on the npm tarball: npm install -g @superdev2347832/agent-bridge ships 1.6.0 built from b2ccc94, one commit ahead of this tag. That commit adds two things not listed below: the OpenCode dialect fix (scanner/writer/doctor now match opencode.ai/docs/mcp-servers — mcp key, local command arrays with environment, remote url servers no longer dropped) and the full-migration sweep (npm run sweep), which validates all 132 agent-pair migrations end-to-end and passed 132/132. 203/203 tests green.

Features

• fix --dry-run — previews every planned auto-fix with before/after content and writes nothing; the same backup-transaction apply path as before when run without the flag
• Honest migrate feedback — migrate/apply/migrate-all surface doctor's config errors (file:line) instead of silently dropping an unparseable source config's servers; healthy projects stay warning-free
• plan and diff validate both agent ids against the registry — diff no longer exits 0 claiming "nothing to do" for an unknown target, and plan's stale 3-agent list is replaced by the full registry-derived list
• scan prints the agent id next to the display name (Detected: Claude Code (id: claude-code)) — the id every other command requires

Fixes

• CLI no longer crashes with EPIPE when output is piped (agent-migrate scan | head)
• Positional-arg parsing is flag-position transparent (migrate s t --dry-run no longer treats the flag as a path)
• Self-migration is rejected with exit 2; nonexistent project paths are an error, not a silent empty migration
• .agentbridge/ backup dirs are gitignored so users' git status stays clean

Docs

• Playtest findings documented; README's command table covers fix --dry-run