Fix ~50 errcheck warnings across the codebase:
- Add explicit `_ =` for intentionally ignored error returns (cleanup,
best-effort operations, etc.)
- Use `defer func() { _ = ... }()` pattern for defer statements
- Handle tmux SetEnvironment, KillSession, SendKeysRaw returns
- Handle mail router.Send returns
- Handle os.RemoveAll, os.Rename in cleanup paths
- Handle rand.Read returns for ID generation
- Handle fmt.Fprint* returns when writing to io.Writer
- Fix for-select with single case to use for-range
- Handle cobra MarkFlagRequired returns
All tests pass. Code compiles without errors.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Add git helper functions for merge request conflict checking:
- FetchBranch(remote, branch): fetch a specific branch from remote
- CheckConflicts(source, target): test merge to detect conflicts
- Returns list of conflicting files without modifying working directory
- runMergeCheck helper to capture stdout (where CONFLICT appears)
Tests cover clean merges, conflicting merges, and working dir cleanup.
Closes gt-3x1.2
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
