feat(search): support platform and benchmark config filters

Add platform handling to submissions and persist a normalized value (`windows`, `linux`, `macos`) with a default of `windows` when omitted.

Extend search/index filtering to support `thread`, `platform`, `intensity`, and `durationSecs` alongside existing text/CPU token matching, and wire these params through request parsing, page data, and navigation URLs.

Update API/README docs and examples to reflect the new submission inputs and search capabilities so users can run more precise queries.feat(search): support platform and benchmark config filters

Add platform handling to submissions and persist a normalized value (`windows`, `linux`, `macos`) with a default of `windows` when omitted.

Extend search/index filtering to support `thread`, `platform`, `intensity`, and `durationSecs` alongside existing text/CPU token matching, and wire these params through request parsing, page data, and navigation URLs.

Update API/README docs and examples to reflect the new submission inputs and search capabilities so users can run more precise queries.

lib/model/submission.go

@@ -60,6 +60,7 @@ type BenchmarkResult struct {
 type Submission struct {
 	SubmissionID string    `json:"submissionID"`
 	Submitter    string    `json:"submitter"`
+	Platform     string    `json:"platform"`
 	SubmittedAt  time.Time `json:"submittedAt"`
 	BenchmarkResult
 }
@@ -111,6 +112,27 @@ func NormalizeSubmitter(submitter string) string {
 	return submitter
 }
 
+func NormalizePlatform(platform string) string {
+	switch strings.ToLower(strings.TrimSpace(platform)) {
+	case "", "windows":
+		return "windows"
+	case "linux":
+		return "linux"
+	case "macos":
+		return "macos"
+	default:
+		return ""
+	}
+}
+
+func ValidatePlatform(platform string) error {
+	if NormalizePlatform(platform) == "" {
+		return errors.New("platform must be one of windows, linux, or macos")
+	}
+
+	return nil
+}
+
 func ThreadModeLabel(multiCore bool) string {
 	if multiCore {
 		return "Multi-threaded"