[proxy] LLM parsers, pricing, and builtin middlewares (OpenAI, Anthropic, Vertex AI, AWS Bedrock)

Request/response parsers and SSE/event-stream metering, the embedded pricing
table, and the builtin middleware set: request parser, router, policy
limit-check/record, cost meter, guardrail, identity inject, response parser.
Includes the path-routed providers — Google Vertex AI (keyfile:: service-account
OAuth minting) and AWS Bedrock (bearer auth, invoke/converse/streaming, optional
/bedrock prefix) — plus the Models allowlist and unmeterable-publisher deny.

proxy/internal/llm/parser_test.go

@@ -0,0 +1,54 @@
+package llm
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestParsers_ProviderNames(t *testing.T) {
+	parsers := Parsers()
+	require.Len(t, parsers, 3, "three built-in parsers expected")
+
+	names := make([]string, 0, len(parsers))
+	for _, p := range parsers {
+		names = append(names, p.ProviderName())
+	}
+	assert.Contains(t, names, "openai", "OpenAI parser should be registered")
+	assert.Contains(t, names, "anthropic", "Anthropic parser should be registered")
+	assert.Contains(t, names, "bedrock", "Bedrock parser should be registered")
+}
+
+func TestDetectParser(t *testing.T) {
+	cases := []struct {
+		name         string
+		path         string
+		expectedName string
+		expectOK     bool
+	}{
+		{"openai chat", "/v1/chat/completions", "openai", true},
+		{"openai prefixed", "/api/v1/chat/completions", "openai", true},
+		{"openai responses", "/v1/responses", "openai", true},
+		{"anthropic messages", "/v1/messages", "anthropic", true},
+		{"anthropic prefixed", "/proxy/v1/messages?query", "anthropic", true},
+		{"unknown path", "/healthz", "", false},
+		{"empty path", "", "", false},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			p, ok := DetectParser(tc.path)
+			require.Equal(t, tc.expectOK, ok, "detection success mismatch for %q", tc.path)
+			if ok {
+				assert.Equal(t, tc.expectedName, p.ProviderName(), "provider name mismatch")
+			}
+		})
+	}
+}
+
+func TestProviderValues(t *testing.T) {
+	assert.Equal(t, Provider(0), ProviderUnknown, "unknown provider is the zero value")
+	assert.Equal(t, ProviderOpenAI, OpenAIParser{}.Provider(), "OpenAI parser reports its provider enum")
+	assert.Equal(t, ProviderAnthropic, AnthropicParser{}.Provider(), "Anthropic parser reports its provider enum")
+}