Allow refining on main with --since parameter, wait on in-progress reviews if any when invoking refine (#53)

**New Features**
- Add `--since` flag to `refine` to limit reviews to commits since a
given ancestor.

**Improvements**
- Wait for in-progress reviews before triggering branch reviews to avoid
duplicate work

Also quite a bit of roborev-driven test coverage

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: wesm

README.md

@@ -95,10 +95,12 @@ Use `refine` to automatically address failed reviews on your branch:
 
 ```bash
 roborev refine                       # Fix failed reviews using default agent
-roborev refine --agent claude-code   # Use specific agent
+roborev refine --agent claude-code   # Use specific agent for addressing findings
 roborev refine --max-iterations 5    # Limit fix attempts
 roborev refine --quiet               # Show elapsed time instead of agent output
 roborev refine --reasoning thorough  # Use thorough reasoning (slower, more accurate)
+roborev refine --since abc123        # Refine commits since a specific commit
+roborev refine --since HEAD~3        # Refine the last 3 commits (works on main branch)
 ```
 
 ```mermaid
@@ -121,7 +123,7 @@ flowchart TD
 
 The loop processes commits oldest-first. When a fix fails review, it keeps addressing that fix until it passes before moving to the next oldest failed commit. Passing reviews are automatically marked as addressed. When no individual failed reviews remain, a whole-branch review runs; if that passes, the refiner exits successfully.
 
-Requires a clean working tree and must not be on the main branch.
+Requires a clean working tree. By default, refine works on feature branches (comparing against main). Use `--since` to refine specific commits on any branch, including main.
 
 ### Security Considerations
 

cmd/roborev/main.go

@@ -900,6 +900,11 @@ Examples:
   roborev respond --job 1234567 "msg"  # Force numeric arg as job ID`,
 		Args: cobra.RangeArgs(1, 2),
 		RunE: func(cmd *cobra.Command, args []string) error {
+			// Ensure daemon is running
+			if err := ensureDaemon(); err != nil {
+				return fmt.Errorf("daemon not running: %w", err)
+			}
+
 			ref := args[0]
 
 			// Check if ref is a job ID (numeric) or SHA