refactor: consolidate duplicate path-finding utilities (bd-74w1, bd-4nqq)

- Add git.GetRepoRoot() with Windows path normalization
- Update beads.findGitRoot() to delegate to git.GetRepoRoot()
- Replace findBeadsDir() with beads.FindBeadsDir() across 8 files
- Remove duplicate findBeadsDir() and findGitRoot() function definitions
- Remove dead test code (TestInfoCommand, TestInfoWithNoDaemon)
- Update tests to work with consolidated APIs

Part of Code Health Review Dec 2025 epic (bd-tggf).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/bd/fork_protection.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 
 	"github.com/steveyegge/beads/internal/debug"
+	"github.com/steveyegge/beads/internal/git"
 )
 
 // ensureForkProtection prevents contributors from accidentally committing
@@ -16,8 +17,8 @@ import (
 // .beads/issues.jsonl to .git/info/exclude so it won't be staged.
 // This is a per-clone setting that doesn't modify tracked files.
 func ensureForkProtection() {
-	// Find git root (reuses existing findGitRoot from autoimport.go)
-	gitRoot := findGitRoot()
+	// Find git root
+	gitRoot := git.GetRepoRoot()
 	if gitRoot == "" {
 		return // Not in a git repo
 	}