Add schema compatibility probe to prevent silent migration failures (bd-ckvw)

- Implement comprehensive schema probe in sqlite.New() that verifies all
  expected tables and columns after migrations
- Add retry logic: if probe fails, retry migrations once
- Return clear fatal error with missing schema elements if probe still fails
- Enhance daemon version gating: refuse RPC if client has newer minor version
- Improve checkVersionMismatch messaging: verify schema before claiming upgrade
- Add schema compatibility check to bd doctor command
- Add comprehensive tests for schema probing

This prevents the silent migration failure bug where:
1. Migrations fail silently
2. Database queries fail with 'no such column' errors
3. Import logic misinterprets as 'not found' and tries INSERT
4. Results in cryptic UNIQUE constraint errors

Fixes #262

Amp-Thread-ID: https://ampcode.com/threads/T-0d7ae2c0-9f12-4f9b-85d1-1291488af150
Co-authored-by: Amp <amp@ampcode.com>

internal/storage/sqlite/sqlite.go

@@ -78,6 +78,21 @@ func New(path string) (*SQLiteStorage, error) {
 		return nil, err
 	}
 
+	// Verify schema compatibility after migrations (bd-ckvw)
+	// First attempt
+	if err := verifySchemaCompatibility(db); err != nil {
+		// Schema probe failed - retry migrations once
+		if retryErr := RunMigrations(db); retryErr != nil {
+			return nil, fmt.Errorf("migration retry failed after schema probe failure: %w (original: %v)", retryErr, err)
+		}
+		
+		// Probe again after retry
+		if err := verifySchemaCompatibility(db); err != nil {
+			// Still failing - return fatal error with clear message
+			return nil, fmt.Errorf("schema probe failed after migration retry: %w. Database may be corrupted or from incompatible version. Run 'bd doctor' to diagnose", err)
+		}
+	}
+
 	// Convert to absolute path for consistency (but keep :memory: as-is)
 	absPath := path
 	if path != ":memory:" {