Phase 6: Permissions + Checkpoints for tri-api

[gHashTag]

Summary

3-level permission system (deny > allow) + git checkpoints before writes.

Permissions

~/.tri-api/settings.json       # user (global)
.tri-api/settings.json         # project (per-repo, overrides user)

Settings format:

{
  "permissions": {
    "allow": ["bash(git diff *)", "bash(zig build *)", "read_file(*)"],
    "deny": ["bash(rm -rf *)", "write_file(.env)", "bash(git push *)"]
  }
}

deny wins over allow (same as Claude Code).

Checkpoints

Git stash snapshot before every write_file tool execution.
/undo command to restore from checkpoint.

Files

File	Action	LOC
src/tri-api/permissions.zig	NEW	~150
src/tri-api/checkpoint.zig	NEW	~100
src/tri-api/tool_executor.zig	MOD	+20
src/tri-api/main.zig	MOD	+10
bot/handlers.zig	MOD	+15

Acceptance Criteria

• deny rules block tool execution
• allow rules permit tool execution
• Project settings override user settings
• Git checkpoint created before every write_file
• /undo restores last checkpoint
• zig build clean

[gHashTag]

Implemented in commit bb07f5e. Phase 6: deny>allow permissions (6/6 tests pass) + git checkpoints before writes + /undo command.