refactor: migrate replicator init output from .opencode/command/ to .opencode/commands/

[marcusburghardt]

Context

OpenCode documentation canonicalizes .opencode/commands/ (plural) as the standard directory for slash commands. OpenSpec already switched (Fission-AI/OpenSpec#748). The unbound-force meta-repo has migrated its scaffold engine in PR unbound-force/unbound-force#164.

Problem

replicator init currently creates command files (forge.md, forge-status.md, handoff.md, inbox.md, org.md) in .opencode/command/ (singular). This creates a split-directory situation when used alongside uf init (which now writes to .opencode/commands/).

OpenCode's runtime loads both directories via a {command,commands} glob, so nothing is functionally broken. But the inconsistency is confusing.

What Needs to Change

1. Update replicator init to write command files to .opencode/commands/ instead of .opencode/command/
2. No migration logic needed in replicator itself -- uf init already handles migration of files left in the old directory

References

• OpenCode docs: https://opencode.ai/docs/commands/
• OpenSpec fix: OpenCode command directory: command/ vs commands/ Fission-AI/OpenSpec#748
• UF migration PR: refactor: migrate .opencode/command/ to .opencode/commands/ unbound-force#164