feat(hyperguild): tier subcommand

Adds the tier subcommand to the hyperguild CLI. Reuses
internal/tier.Detect verbatim, sources probe URLs from
ANTHROPIC_PROBE_URL (default https://api.anthropic.com) and
LITELLM_BASE_URL (no default — empty triggers airplane).

Human-readable output by default; --json emits the same Info struct
as the supervisor's tier MCP returns. Tests cover all three tier
states via httptest fakes.

cmd/hyperguild/main_test.go

@@ -35,8 +35,8 @@ func TestDispatch_UnknownSubcommand_ReturnsTwo(t *testing.T) {
 
 func TestDispatch_KnownSubcommand_RoutesAndReturnsExitCode(t *testing.T) {
 	var out, errBuf bytes.Buffer
-	code := dispatch(context.Background(), []string{"tier"}, strings.NewReader(""), &out, &errBuf)
-	// At Task 1 time, tier returns the not-implemented error → exit 1.
+	code := dispatch(context.Background(), []string{"brain"}, strings.NewReader(""), &out, &errBuf)
+	// At this point, brain still returns the not-implemented error → exit 1.
 	assert.Equal(t, 1, code)
 	assert.Contains(t, errBuf.String(), "not implemented")
 }